Point-to-point protocol encapsulation in ethernet frame

ABSTRACT

A wireless data network which provides communications with a Pier to Pier Protocol server is disclosed. The network includes a home network that includes a home mobile switching center, a wireless modem and one or more end system. The wireless modem and the end systems are connected together via an ethernet link. The network also includes a PPP server, wherein PPP information sent from PPP server for the end systems is encapsulated by the wireless modem in an ethernet frame and sent to the end systems via the ethernet link.

[0001] Priority benefit of the Oct. 14, 1997 filing date of provisionalapplication serial number 60/061,915 is hereby claimed.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a wireless data network, andmore particularly to communicating with a Pier to Pier Protocol serverin the wireless data network.

[0004] 2. Description of Related Art

[0005]FIG. 1 depicts three business entities, whose equipment, workingtogether typically provide remote internet access to user computers 2through user modems 4. User computers 2 and modems 4 constitute endsystems.

[0006] The first business entity is the telephone company (telco) thatowns and operates the dial-up plain old telephone system (POTS) orintegrated services data network (ISDN) network. The telco provides themedia in the form of public switched telephone network (PSTN) 6 overwhich bits (or packets) can flow between users and the other twobusiness entities.

[0007] The second business entity is the internet service provider(ISP). The ISP deploys and manages one or more points of presence (POPs)8 in its service area to which end users connect for network service. AnISP typically establishes a POP in each major local calling area inwhich the ISP expects to subscribe customers. The POP converts messagetraffic from the PSTN run by the telco into a digital form to be carriedover intranet backbone 10 owned by the ISP or leased from an intranetbackbone provider like MCI, Inc. An ISP typically leases fractional orfull T1 lines or fractional or full T3 lines from the telco forconnectivity to the PSTN. The POPs and the ISP's medium data center 14are connected together over the intranet backbone through router 12A.The data center houses the ISP's web servers, mail servers, accountingand registration servers, enabling the ISP to provide web content,e-mail and web hosting services to end users. Future value addedservices may be added by deploying additional types of servers in thedata center. The ISP also maintains router 12A to connect to publicinternet backbone 20. In the current model for remote access, end usershave service relationships with their telco and their ISP and usuallyget separate bills from both. End users access the ISP, and through theISP, public internet 20, by dialing the nearest POP and running acommunication protocol known as the Internet Engineering Task Force(IETF) point-to-point protocol (PPP).

[0008] The third business entity is the private corporation which ownsand operates its own private intranet 18 through router 12B for businessreasons. Corporate employees may access corporate network 18 (e.g., fromhome or while on the road) by making POTS/ISDN calls to corporate remoteaccess server 16 and running the IETF PPP protocol. For corporateaccess, end users only pay for the cost of connecting to corporateremote access server 16. The ISP is not involved. The privatecorporation maintains router 12B to connect an end user to eithercorporate intranet 18 or public internet 20 or both.

[0009] End users pay the telco for the cost of making phone calls andfor the cost of a phone line into their home. End users also pay the ISPfor accessing the ISP's network and services. The present invention willbenefit wireless service providers like Sprint PCS, PrimeCo, etc. andbenefit internet service providers like AOL, AT&T Worldnet, etc.

[0010] Today, internet service providers offer internet access services,web content services, e-mail services, content hosting services androaming to end users. Because of low margins and no scope of doingmarket segmentation based on features and price, ISPs are looking forvalue added services to improve margins. In the short term, equipmentvendors will be able to offer solutions to ISPs to enable them to offerfaster access, virtual private networking (which is the ability to usepublic networks securely as private networks and to connect tointranets), roaming consortiums, push technologies and quality ofservice. In the longer term, voice over internet and mobility will alsobe offered. ISPs will use these value added services to escape from thelow margin straitjacket. Many of these value added services fall in thecategory of network services and can be offered only through the networkinfrastructure equipment. Others fall in the category of applicationservices which require support from the network infrastructure, whileothers do not require any support from the network infrastructure.Services like faster access, virtual private networking, roaming,mobility, voice, quality of service, quality of service based accountingall need enhanced network infrastructure. The system described here willbe either directly provide these enhanced services or provide hooks sothat these services can be added later as future enhancements. Wirelessservice providers will be able to capture a larger share of the revenuestream. The ISP will be able to offer more services and with bettermarket segmentation.

SUMMARY OF THE INVENTION

[0011] The present invention provides end users with remote wirelessaccess to the public internet, private intranets and internet serviceproviders. Wireless access is provided through base stations in a homenetwork and base stations in foreign networks with interchangeagreements.

[0012] It is an object of the present system to provide a wirelesspacket switched data network for end users that divides mobilitymanagement into local, micro, macro and global connection handovercategories and minimizes handoff updates according to the handovercategory. It is another object to integrate MAC handoff messages withnetwork handoff messages. It is a further object of the present systemto separately direct registration functions to a registration server anddirect routing functions to inter-working function units. It is yetanother object to provide an intermediate XTunnel channel between awireless hub (also called access hub AH) and an inter-working functionunit (IWF unit) in a foreign network. It is yet another object toprovide an IXTunnel channel between an inter-working function unit in aforeign network and an inter-working function unit in a home network. Itis yet another object to enhance the layer two tunneling protocol (L2TP)to support a mobile end system. It is yet another object to performnetwork layer registration before the start of a PPP communicationsession.

[0013] According to one embodiment of the invention, a wireless datanetwork which provides communications with a Pier to Pier Protocolserver is disclosed. The network includes a home network that includes ahome mobile switching center, a wireless modem and one or more endsystem. The wireless modem and the end systems are connected togethervia an ethernet link. The network also includes a PPP server, whereinPPP information sent from PPP server for the end systems is encapsulatedby the wireless modem in an ethernet frame and sent to the end systemsvia the ethernet link.

BRIEF DESCRIPTION OF DRAWINGS

[0014] The system will be described in detail in the followingdescription of preferred embodiments with reference to the followingfigures wherein:

[0015]FIG. 1 is a configuration diagram of a known remote accessarchitecture through a public switched telephone network;

[0016]FIG. 2 is a configuration diagram of a remote access architecturethrough a wireless packet switched data network according to the presentinvention;

[0017]FIG. 3 is a configuration diagram of selected parts of thearchitecture of the network of FIG. 2 showing a roaming scenario;

[0018]FIG. 4 is a configuration diagram of a base station with localaccess points;

[0019]FIG. 5 is a configuration diagram of a base station with remoteaccess points;

[0020]FIG. 6 is a configuration diagram of a base station with remoteaccess points, some of which are connected using a wireless trunkconnection;

[0021]FIG. 7 is a diagram of a protocol stack for a local access point;

[0022]FIG. 8 is a diagram of a protocol stack for a remote access pointwith a wireless trunk;

[0023]FIG. 9 is a diagram of a protocol stack for a relay function inthe base station for supporting remote access points with wirelesstrunks;

[0024]FIG. 10 is a diagram of protocol stacks for implementing the relayfunction depicted in FIG. 9;

[0025]FIG. 11 is a diagram of protocol stacks for a relay function inthe base station for supporting local access points;

[0026]FIG. 12 is a configuration diagram of selected parts of thearchitecture of the network of FIG. 2 showing a first end systemregistering in the home network from the home network and a secondsystem registering in the home network from a foreign network using ahome inter-working function for an anchor;

[0027]FIG. 13 is a configuration diagram of selected parts of thearchitecture of the network of FIG. 2 showing a first end systemregistering in the home network from the home network and a secondsystem registering in the home network from a foreign network using aserving inter-working function for an anchor;

[0028]FIG. 14 is a ladder diagram of the request and response messagesto register in a home network from a foreign network and to establish,authenticate and configure a data link;

[0029]FIG. 15 is a configuration diagram of selected parts of thearchitecture of the network of FIG. 2 showing registration requests andresponses for registering a mobile in a home network from the homenetwork;

[0030]FIG. 16 is a configuration diagram of selected parts of thearchitecture of the network of FIG. 2 showing registration requests andresponses for registering a mobile in a home network from a foreignnetwork;

[0031]FIG. 17 is a configuration diagram of protocol stacks showingcommunications between an end system in a home network and aninter-working function in the home network where the cell site has localaccess points;

[0032]FIG. 18 is a configuration diagram of protocol stacks showingcommunications between an end system in a home network and aninter-working function in the home network where the cell site hasremote access points coupled to a wireless hub through a wireless trunk;

[0033]FIG. 19 is a configuration diagram of protocol stacks showingcommunications between a base station coupled to a roaming end systemand a home inter-working function;

[0034]FIG. 20 is a configuration diagram of protocol stacks showingcommunications between an end system in a home network through aninter-working function in the home network to an internet serviceprovider;

[0035]FIG. 21 is a configuration diagram of protocol stacks showingcommunications between an end system in a foreign network and a homeregistration server in a home network during the registration phase;

[0036]FIG. 22 is a processing flow diagram showing the processing ofaccounting data through to the customer billing system;

[0037]FIGS. 23 and 24 are ladder diagrams depicting the registrationprocess for an end system in a home network and in a foreign network,respectively;

[0038]FIGS. 25 and 26 are protocol stack diagrams depicting an endsystem connection in a home network where a PPP protocol terminates inan inter-working function of the home network and where the PPP protocolterminates in an ISP or intranet, respectively;

[0039]FIGS. 27 and 28 are protocol stack diagrams depicting an endsystem connection in a foreign network where a PPP protocol terminatesin an inter-working function of the foreign network and where the PPPprotocol terminates in an ISP or intranet, respectively;

[0040]FIG. 29 illustrates end systems connected via ethernet to awireless modem where PPP protocol is encapsulated in an ethernet frame;

[0041]FIG. 30 illustrates an ethernet frame format;

[0042]FIG. 31 illustrates XWD Header fields;

[0043]FIG. 32 illustrates end systems connected via a local area networkto a wireless router where PPP protocol terminates at the wirelessrouter;

[0044]FIGS. 33, 34 and 35 are ladder diagrams depicting a local handoffscenario, a micro handoff scenario and a macro handoff scenario,respectively;

[0045]FIG. 36 is a ladder diagram depicting a global handoff scenariowhere the foreign registration server changes and where homeinter-working function does not change; and

[0046]FIG. 37 is a ladder diagram depicting a global handoff scenariowhere both the foreign registration server and the home inter-workingfunction change.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0047] The present system provides computer users with remote access tothe internet and to private intranets using virtual private networkservices over a high speed, packet switched, wireless data link. Theseusers are able to access the public internet, private intranets andtheir internet service providers over a wireless link. The networksupports roaming, that is, the ability to access the internet andprivate intranets using virtual private network services from anywherethat the services offered by the present system are available. Thenetwork also supports handoffs, that is, the ability to change the pointof attachment of the user to the network without disturbing the PPP linkbetween the PPP client and the PPP server. The network targets usersrunning horizontal internet and intranet applications. Theseapplications include electronic mail, file transfer, browser based WWWaccess and other business applications built around the internet.Because the network will be based on the IETF standards, it is possibleto run streaming media protocols like RTP and conferencing protocolslike H.323 over it.

[0048] Other internet remote access technologies that are alreadydeployed or are in various stages of deployment include: wire linedial-up access based on POTS and ISDN, XDSL access, wireless circuitswitched access based on GSM/CDMA/TDMA, wireless packet switched accessbased on GSM/CDMA/TDMA, cable modems, and satellite based systems.However, the present system offers a low cost of deployment, ease ofmaintenance, a broad feature set, scaleability, an ability to degradegracefully under heavy load conditions and support for enhanced networkservices like virtual private networking, roaming, mobility and qualityof service to the relative benefit of users and service providers.

[0049] For wireless service providers who own personal communicationssystem (PCS) spectrum, the present system will enable them to offerwireless packet switched data access services that can compete withservices provided by the traditional wire line telcos who own andoperate the PSTN. Wireless service providers may also decide to becomeinternet service providers themselves, in which case, they will own andoperate the whole network and provide end to end services to users.

[0050] For internet service providers the present system will allow themto by-pass the telcos (provided they purchase or lease the spectrum) andoffer direct end to end services to users, perhaps saving access chargesto the telcos, which may increase in the future as the internet grows tobecome even bigger than it is now.

[0051] The present systems flexible so that it can benefit wirelessservice providers who are not internet service providers and who justprovide ISP, internet or private intranet access to end users. Thesystem can also benefit service providers who provide wireless accessand internet services to end users. The system can also benefit serviceproviders who provide wireless access and internet services but alsoallow the wireless portion of the network to be used for access to otherISPs or to private intranets.

[0052] In FIG. 2, end systems 32 (e.g., based on, for example, Win 95personal computer) connect to wireless network 30 using external orinternal modems. These modems allow end systems to send and receivemedium access control (MAC) frames over air link 34. External modemsattach to the PC via a wired or wireless link. External modems arefixed, and, for example, co-located with roof top mounted directionalantennae. External modems may be connected to the user's PC using anyone of following means: 802.3, universal serial bus, parallel port,infra-red, or even an ISM radio link. Internal modems are preferablyPCMCIA cards for laptops and are plugged into the laptop's backplane.Using a small omni-directional antenna, they send and receive MAC framesover the air link. End systems can also be laptops with a directionalantenna, a fixed wireless station in a home with a directional antennaconnected via AC lines, and other alternatives.

[0053] Wide-area wireless coverage is provided by base stations 36. Thebase station 36 can employ a 5-channel reuse communication scheme asdescribed in U.S. patent application Ser. No. 08/998,505, filed on Dec.26, 1997. The range of coverage provided by base stations 36 depends onfactors like link budget, capacity and coverage. Base stations aretypically installed in cell sites by PCS (personal communicationservices) wireless service providers. Base stations multiplex end systemtraffic from their coverage area to the system's mobile switching center(MSC) 40 over wire line or microwave backhaul network 38.

[0054] The system is independent of the MAC and PHY (physical) layer ofthe air link and the type of modem. The architecture is also independentof the physical layer and topology of backhaul network 38. The onlyrequirements for the backhaul network are that it must be capable ofrouting internet protocol (IP) packets between base stations and the MSCwith adequate performance. At Mobile Switching Center 40 (MSC 40),packet data inter-working function (IWF) 52 terminates the wirelessprotocols for this network. IP router 42 connects MSC 40 to publicinternet 44, private intranets 46 or to internet service providers 46.Accounting and directory servers 48 in MSC 40 store accounting data anddirectory information. Element management server 50 manages theequipment which includes the base stations, the IWFs andaccounting/directory servers.

[0055] The accounting server will collect accounting data on behalf ofusers and send the data to the service provider's billing system. Theinterface supported by the accounting server will send accountinginformation in American Management Association (AMA) billing recordformat, or any other suitable billing format, over a TCP/IP (transportcontrol protocol/internet protocol) transport to the billing system(which is not shown in the figure).

[0056] The network infrastructure provides PPP (point-to-point protocol)service to end systems. The network provides (1) fixed wireless accesswith roaming (log-in anywhere that the wireless coverage is available)to end systems and (2) low speed mobility and hand-offs. When an endsystem logs on to a network, in it may request either fixed service(i.e., stationary and not requiring handoff services) or mobile service(i.e., needing handoff services). An end system that does not specifyfixed or mobile is regarded as specifying mobile service. The actualregistration of the end system is the result of a negotiation with ahome registration server based on requested level of service, the levelof services subscribed to by the user of the end system and thefacilities available in the network.

[0057] If the end system negotiates a fixed service registration (i.e.,not requiring handoff services) and the end system is located in thehome network, an IWF (inter-working function) is implemented in the basestation to relay traffic between the end user and a communicationsserver such as a PPP server (i.e., the point with which to be connected,for example, an ISP PPP server or a corporate intranet PPP server or aPPP server operated by the wireless service provider to providecustomers with direct access to the public internet). It is anticipatedthat perhaps 80% of the message traffic will be of this category, andthus, this architecture distributes IWF processing into the basestations and avoids message traffic congestion in a central mobileswitching center.

[0058] If the end system requests mobile service (from a home network ora foreign network) or if the end system request roaming service (i.e.,service from the home network through a foreign network), two IWFs areestablished: a serving IWF typically established in the base station ofthe network to which the end system is attached (be it the home networkor a foreign network) and a home IWF typically established in mobileswitching center MSC of the home network. Since this situation isanticipated to involve only about 20% of the message traffic, themessage traffic congestion around the mobile switching center isminimized. The serving IWF and the wireless hub may be co-located in thesame nest of computers or may even be programmed in the same computer sothat a tunnel using an XTunnel protocol need not be established betweenthe wireless hub and the serving IWF.

[0059] However, based on available facilities and the type and qualityof service requested, a serving IWF in a foreign network mayalternatively be chosen from facilities in the foreign MSC. Generally,the home IWF becomes an anchor point that is not changed during thecommunications session, while the serving IWF may change if the endsystem moves sufficiently.

[0060] The base station includes an access hub and at least one accesspoint (be it remote or collocated with the access hub). Typically, theaccess hub serves multiple access points. While the end system may beattached to an access point by a wire or cable according to theteachings of this invention, in a preferred embodiment the end system isattached to the access point by a wireless “air link”, in which case theaccess hub is conveniently referred to as a wireless hub. While theaccess hub is referred to as a “wireless hub” throughout the descriptionherein, it will be appreciated that an end system coupled through anaccess point to an access hub by wire or cable is an equivalentimplementation and is contemplated by the term “access hub”.

[0061] In the invention, an end system includes an end user registrationagent (e.g., software running on a computer of the end system, its modemor both) that communicates with an access point, and through the accesspoint to a wireless hub. The wireless hub includes a proxy registrationagent (e.g., software running on a processor in the wireless hub) actingas a proxy for the end user registration agent. Similar concepts usedin, for example, the IETF proposed Mobile IP standard are commonlyreferred to as a foreign agent (FA). For this reason, the proxyregistration agent of the present system will be referred to as aforeign agent, and aspects of the foreign agent of the present systemthat differ from the foreign agent of Mobile IP are as describedthroughout this description.

[0062] Using the proxy registration agent (i.e., foreign agent FA) in abase station, the user registration agent of an end system is able todiscover a point of attachment to the network and register with aregistration server in the MSC (mobile switching center) of the homenetwork. The home registration server determines the availability ofeach of the plural inter-working function modules (IWFs) in the network(actually software modules that run on processors in both the MSC andthe wireless hubs) and assigns IWF(s) to the registered end system. Foreach registered end system, a tunnel (using the XTunnel protocol) iscreated between the wireless hub in the base station and aninter-working function (IWF) in the mobile switching center (MSC), thistunnel transporting PPP frames between the end system and the IWF.

[0063] As used herein, the XTunnel protocol is a protocol that providesin-sequence transport of PPP data frames with flow control. Thisprotocol may run over standard IP networks or over point-to-pointnetworks or over switched networks like ATM data networks or frame relaydata networks. Such networks may be based on T1 or T3 links or based onradio links, whether land based or space based. The XTunnel protocol maybe built by adapting algorithms from L2TP (level 2 transport protocol).In networks based on links where lost data packets may be encountered, are-transmission feature may be a desirable option.

[0064] The end system's PPP peer (i.e., a communications server) mayreside in the IWF or in a corporate intranet or ISP's network. When thePPP peer resides in the IWF, an end system is provided with directinternet access. When the PPP peer resides in an intranet or ISP, an endsystem is provided with intranet access or access to an ISP. In order tosupport intranet or ISP access, the IWF uses the layer two tunnelingprotocol (L2TP) to connect to the intranet or ISP's PPP server. From thepoint of view of the intranet or ISP's PPP server, the IWF looks like anetwork access server (NAS). PPP traffic between the end system and theIWF is relayed by the foreign agent in the base station.

[0065] In the reverse (up link) direction, PPP frames traveling from theend system to the IWF are sent over the MAC and air link to the basestation. The base station relays these frames to the IWF in the MSCusing the XTunnel protocol. The IWF delivers them to a PPP server forprocessing. For internet access, the PPP server may be in the samemachine as the IWF. For ISP or intranet access, the PPP server is in aprivate network and the IWF uses the layer two tunneling protocol (L2TP)to connect to it.

[0066] In the forward (down link) direction, PPP frames from the PPPserver are relayed by the IWF to the base station using the XTunnelprotocol. The base station de-tunnels down link frames and relays themover the air link to the end system, where they are processed by the endsystem's PPP layer.

[0067] To support mobility, support for hand-offs are included. The MAClayer assists the mobility management software in the base station andthe end system to perform hand-offs efficiently. Hand-offs are handledtransparently from the peer PPP entities and the L2TP tunnel. If an endsystem moves from one base station to another, a new XTunnel is createdbetween the new base station and the original IWF. The old XTunnel fromthe old base station will be deleted. PPP frames will transparentlytraverse the new path.

[0068] The network supports roaming (i.e., when the end user connects toits home wireless service provider through a foreign wireless serviceprovider). Using this feature, end systems are able to roam away fromthe home network to a foreign network and still get service, provided ofcourse that the foreign wireless service provider and the end system'shome wireless service provider have a service agreement.

[0069] In FIG. 3, roaming end system 60 has traveled to a location atwhich foreign wireless service provider 62 provides coverage. However,roaming end system 60 has a subscriber relationship with home wirelessservice provider 70. In the present invention, home wireless serviceprovider 70 has a contractual relationship with foreign wireless serviceprovider 62 to provide access services. Therefore, roaming end system 60connects to base station 64 of foreign wireless service provider 62 overthe air link. Then, data is relayed from roaming end system 60 throughbase station 64, through serving IWF 66 of foreign wireless serviceprovider 62, to home IWF 72 of home wireless service provider 70, orpossibly through home IWF 72 of home wireless service provider 70 tointernet service provider 74.

[0070] An inter-service provider interface, called the I-interface, isused for communications across wireless service provider (WSP)boundaries to support roaming. This interface is used forauthenticating, registering and for transporting the end system's PPPframes between the foreign WSP and the home WSP.

[0071] PPP frames in the up link and the down link directions travelthrough the end system's home wireless service provider (WSP).Alternatively, PPP frames directly transit from the foreign WSP to thedestination network. The base station in the foreign WSP is the endsystem's point of attachment in the foreign network. This base stationsends (and receives) PPP frames to (and from) a serving IWF in theforeign WSP's mobile switching center. The serving IWF connects over theI-interface to the home IWF using a layer two tunnel to transport theend system's PPP frames in both directions. The serving IWF in theforeign WSP collects accounting data for auditing The home IWF in thehome WSP collects accounting data for billing.

[0072] The serving IWF in the foreign WSP may be combined with the basestation in the same system, thus eliminating the need for the X-Tunnel.

[0073] During the registration phase, a registration server in theforeign WSP determines the identity of the roaming end system's homenetwork. Using this information, the foreign registration servercommunicates with the home registration server to authenticate andregister the end system. These registration messages flow over theI-interface. Once the end system has been authenticated and registered,a layer two tunnel is created between the base station and the servingIWF using the XTUNNEL protocol and another layer two tunnel is createdbetween the serving IWF and the home IWF over the I-interface. The homeIWF connects to the end system's PPP peer as before, using L2TP (level 2tunnel protocol). During hand-offs, the location of the home IWF and theL2TP tunnel remains fixed. As the end system moves from one base stationto another base station, a new tunnel is created between the new basestation and the serving IWF and the old tunnel between the old basestation and the serving IWF is deleted. If the end system moves farenough, so that a new serving IWF is needed, a new tunnel will becreated between the new serving IWF and the home IWF. The old tunnelbetween the old serving and the home will be deleted.

[0074] To support roaming, the I-interface supports authentication,registration and data transport services across wireless serviceprovider boundaries. Authentication and registration services aresupported using the IETF Radius protocol. Data transport services totransfer PPP frames over a layer two tunnel are supported using theIXTunnel protocol. This protocol is based on the IETF L2TP protocol.

[0075] As used in this description, the term home IWF refers to the IWFin the end system's home network. The term serving IWF refers to the IWFin the foreign network which is temporarily providing service to the endsystem. Similarly, the term home registration server refers to theregistration server in the end system's home network and the termforeign registration server refers to the registration server in theforeign network through which the end system registers while it isroaming.

[0076] The network supports both fixed and dynamic IP address assignmentfor end systems. There are two types of IP addresses that need to beconsidered. The first is the identity of the end system in its homenetwork. This may be a structured user name in the format user@domain.This is different from the home IP address used in mobile IP. The secondaddress is the IP address assigned to the end system via the PPP IPCPaddress negotiation process. The domain sub-field of the home address isused to identify the user's home domain and is a fully qualified domainname. The user sub-field of the home address is used to identify theuser in the home domain. The User-Name is stored on the end system andin the subscriber data-base at the MSC and is assigned to the user whenhe or she subscribes to the service. The domain sub-field of theUser-Name is used during roaming to identify roaming relationships andthe home registration server for purposes of registration andauthentication. Instead of the structured user name another uniqueidentifier may be used to identify the user's home network and theuser's identity in the home network. This identifier is sent in theregistration request by the end system The PPP IPCP is used to negotiatethe IP address for the end system. Using IP configuration protocol IPCP,the end system is able to negotiate a fixed or dynamic IP address.

[0077] Although the use of the structured user-name field and thenon-use of an IP address as the home address is a feature thatcharacterizes the present system over a known mobile IP, the network maybe enhanced to also support end systems that have no user-name and onlya non-null home address, if mobile IP and its use in conjunction withPPP end systems becomes popular. The PPP server may be configured by theservice provider to assign IP addresses during the IPCP addressassignment phase that are the same as the end system's home IP address.In this case, the home address and the IPCP assigned IP address will beidentical.

[0078] In FIG. 4, base station 64 and air links from end systems formwireless sub-network 80 that includes the air links for end user access,at least one base station (e.g., station 64) and at least one backhaulnetwork (e.g., 38 of FIG. 2) from the base station to MSC 40 (FIG. 2).The wireless sub-network architecture of, for example, a 3-sectored basestation includes the following logical functions.

[0079] 1. Access point function. Access points 82 perform MAC layerbridging and MAC layer association and dissociation procedures. Anaccess point includes a processor (preferably in the form of customapplication specific integrated circuit ASIC), a link to a wireless hub(preferably in the form of an Ethernet link on a card or built into theASIC), a link to an antenna (preferably in the form of a card with adata modulator/demodulator and a transmitter/receiver), and the antennato which the end system is coupled. The processor runs software toperform a data bridging function and various other functions in supportof registration and mobility handovers as further described herein. Seediscussion with respect to FIGS. 7, 8 and 11.

[0080] Access points (APs) take MAC layer frames from the air link andrelay them to a wireless hub and vice versa. The MAC layer associationand disassociation procedures are used by APs to maintain a list of endsystem MAC addresses in their MAC address filter table. An AP will onlyperform MAC layer bridging on behalf of end systems whose MAC addressesare present in the table. An access point and its associated wirelesshub are typically co-located. In its simplest form, an access point isjust a port into a wireless hub. When the APs and the wireless hub areco-located in the same cell site, they may be connected together via aIEEE 802.3 link. Sometimes, access points are located remotely from thewireless hub and connected via a long distance link like a wired T1trunk or even a wireless trunk. For multi-sector cells, multiple accesspoints (i.e., one per sector) are used.

[0081] 2. Wireless hub function. Wireless hub 84 performs the foreignagent (FA) procedures, backhaul load balancing (e.g., over multipleT1's), backhaul network interfacing, and the xtunnel procedures. Whensupport for quality of service (QOS) is present, the wireless hubimplements the support for QOS by running the xtunnel protocol overbackhauls with different QOS attributes. In a multi-sector cell site, asingle wireless hub function is typically shared by multiple accesspoints.

[0082] A wireless hub includes a processor, a link to one or more accesspoints (preferably in the form of an Ethernet link on a card or builtinto an ASIC), and a link to a backhaul line. The backhaul line istypically a T1 or T3 communications line that terminates in the mobileswitching center of the wireless service provider. The link to thebackhaul line formats data into a preferred format, for example, anEthernet format, a frame relay format or an ATM format. The wireless hubprocessor runs software to support data bridging and various otherfunctions as described herein. See discussion with respect to FIGS. 9,10 and 11.

[0083] The base station design supports the following types of cellarchitectures.

[0084] 1. Local AP architecture. In a local AP architecture, accesspoints have a large (>=2 km, typically) range. They are co-located inthe cell site with the wireless hub (FIG. 4). Access points may beconnected to the wireless hub using an IEEE 802.3 network or may bedirectly plugged into the wireless hub's backplane or connected to thewireless hub using some other mechanism (e.g. universal serial bus,printer port, infra-red, etc.). It will be assumed that the firstalternative is used for the rest of this discussion. The cell site maybe omni or sectored by adding multiple access points and sectoredantennas to a wireless hub.

[0085] 2. Remote AP architecture. In a remote AP architecture, accesspoints usually have a very small range, typically around 1 km radius.They are located remotely (either indoors or outdoors) from the wirelesshub. A T1 or a wireless trunk preferably links remote access points tothe cell site where the wireless hub is located. From the cell site, awire line backhaul or a microwave link is typically used to connect tothe IWF in the MSC. If wireless trunking between the remote AP and thewireless hub is used, omni or sectored wireless radios for trunking areutilized. The devices for trunking to remote access points arepreferably co-located with the wireless hub and may be connected to itusing an IEEE 802.3 network or may be directly plugged into the wirelesshub's backplane. These devices will be referred to by the term trunk AP.

[0086] 3. Mixed AP architecture. In a mixed architecture, the wirelesssub-network will have to support remote and local access points. Remoteaccess points may be added for hole filling and other capacity reasons.As described earlier, T1 or wireless trunks may be used to connect theremote AP to the wireless hub.

[0087]FIG. 5 shows a cell with three sectors using local APs only. Theaccess points and the wireless hub are co-located in the base stationand are connected to each other with 802.3 links.

[0088]FIG. 6 shows an architecture with remote access points 82connected to wireless hub 84 using wireless trunks 86. Each trunk accesspoint in the base station provides a point to multi-point wireless radiolink to the remote micro access points (R-AP in figure). The remoteaccess points provide air link service to end systems. The wireless huband the trunk access points are co-located in the base station andconnected together via 802.3 links. This figure also shows remote accesspoints 82R connected to the wireless hub via point to point T1 links. Inthis scenario, no trunk APs are required.

[0089] To support all of the above cell architectures and the differenttypes of access points that each cell might use, the networkarchitecture follows the following rules:

[0090] 1. Access points function as MAC layer bridges. Remote accesspoints perform MAC bridging between the air link to the end systems andthe wireless or T1 trunk to the cell site. Local access points performMAC bridging between the air link to the end systems and the wirelesshub.

[0091] 2. Trunk access points also function as MAC layer bridges. Theyperform MAC bridging between the trunk (which goes to the access points)and the wireless hub.

[0092] 3. The wireless hub is connected to all co-located MAC bridges(i.e. local access points or trunk access points) using a 802.3 linkinitially.

[0093] Additionally, where local access points or remote access pointswith T1 trunks are used, the following rules are followed.

[0094] 1. Local access points are co-located with the wireless hub andconnected to it using point to point 802.3 links or a shared 802.3network. Remote access points are connected to the wireless hub usingpoint to point T1 trunks.

[0095] 2. Sectorization is supported by adding access points withsectored antennas to the cell site.

[0096] 3. For each access point connected to the wireless hub, there isa foreign agent executing in the wireless hub which participates in endsystem registration. MAC layer association procedures are used to keepthe MAC address filter tables of the access points up to date and toperform MAC layer bridging efficiently. The wireless hub participates inMAC association functions so that only valid MAC addresses are added tothe MAC address filter tables of the access points.

[0097] 4. The foreign agent in the wireless hub relays frames from theaccess points to the MSC IWF and vice versa using the xtunnel protocol.The MAC address filter table is used to filter out those unicast MACdata frames whose MAC addresses are not present in the table. The APsalways forward MAC broadcast frames and MAC frames associated with endsystem registration functions regardless of the contents of the MACaddress filter table.

[0098] 5. Local access points use ARP to resolve MAC addresses forrouting IP traffic to the wireless hub. Conversely, the wireless hubalso uses ARP to route IP packets to access points. UDP/IP is used fornetwork management of access points.

[0099] 6. Remote access points connected via T1 do not use ARP since thelink will be a point to point link.

[0100] 7. Support for hand-offs is done with assistance from the MAClayer.

[0101] In a cell architecture using wireless trunks and trunk APs, thefollowing rules are followed.

[0102] 1. Trunk access points are co-located with the wireless hub andconnected to it using point to point 802.3 links or other suitablemeans.

[0103] 2. Wireless trunk sectorization is supported by adding trunkaccess points with sectored antennas to the cell site.

[0104] 3. Hand-offs across backhaul sectors are done using the foreignagent in the wireless hub. For each backhaul sector, there is a foreignagent executing in the wireless hub.

[0105] 4. The trunk APs do not need to participate in MAC layer endsystem association and hand off procedures. Their MAC address filtertables will be dynamically programmed by the wireless hub as end systemsregister with the network. The MAC address filter table is used tofilter out unicast MAC frames. Broadcast MAC frames or MAC framescontaining registration packets are allowed to always pass through.

[0106] 5. Trunk APs use ARP to resolve MAC addresses for routing IPtraffic to the wireless hub. Conversely, the wireless hub use ARP toroute IP packets to trunk APs. UDP/IP is used for network management oftrunk APs.

[0107] 6. In a single wireless trunk sector, MAC association andhand-offs from one access point to another is done using the MAC layerwith the assistance of the foreign agent in the wireless hub. Usingthese MAC layer procedures, end systems associate with access points. Asend systems move from one access point to another access point, theaccess points will use a MAC hand off protocol to update their MACaddress filter tables. The wireless hub at the cell site providesassistance to access points to perform this function. This assistanceincludes relaying MAC layer hand off messages (since access points willnot be able to communicate directly over the MAC layer with each other)and authenticating the end system for MAC layer registration and handoff and for updating the MAC address filter tables of the access points.

[0108] 7. The foreign agent for a wireless trunk sector is responsiblefor relaying frames from its trunk AP to the MSC and vice versa usingthe xtunnel protocol. Thus, the foreign agent for a trunk AP does notcare about the location of the end system with respect to access pointswithin that wireless trunk sector. In the down link direction, it justforwards frames from the tunnel to the appropriate trunk AP which usesMAC layer bridging to send the frames to all the remote access pointsattached in that backhaul sector. The access points consult their MACaddress filter tables and either forward the MAC frames over the accessnetwork or drop the MAC frames. As described above, the MAC addressfilter tables are kept up to date using MAC layer association and handoff procedures. In the up link direction, MAC frames are forwarded bythe access points to the backhaul bridge which forwards them to theforeign agent in the wireless hub using the 802.3 link.

[0109] 8. ARP is not be used for sending or receiving IP packets to theremote access points. The access points determines the MAC address ofthe wireless hub using BOOTP procedures. Conversely, the wireless hub isconfigured with the MAC address of remote access points. UDP/IP is usedfor network management of access points and for end system associationand hand off messages.

[0110] IEEE Standard 802.3 links in the cell site may be replaced byother speed links.

[0111]FIG. 7 shows the protocol stack for a local access point. At thebase of the stack is physical layer PHY. Physical layer PHY carries datato and from an end system over the air using radio waves as an example.When received from an end system, the AP receives data from the physicallayer and unpacks it from the MAC frames (the MAC layer). The end systemdata frames are then repacked into an Ethernet physical layer format(IEEE 802.3 format) where it is send via the Ethernet link to thewireless hub. When the AP's processor receives data from the wirelesshub via its Ethernet link (i.e., the physical layer), the data to betransmitted to an end system, the AP packs the data in a medium accesscontrol (MAC) format, and sends the MAC layer data to its modulator tobe transmitted to the end system using the PHY layer.

[0112] In FIG. 8, the MAC and PHY layers to/from the end system of FIG.7 are replaced by a MAC and PHY for the trunk to the cell site for aremote access point. Specifically, for a T1 trunk, the high level datalink control protocol (HDLC protocol) is preferably used over the T1.

[0113]FIG. 9 depicts the protocol stack for the wireless hub thatbridges the backhaul line and the trunk to the remote access point. Thetrunk to the remote APs are only required to support remote accesspoints (as distinct from Ethernet coupled access points). The MAC andPHY layers for the wireless trunk to the remote APs provide a point tomultipoint link so that one trunk may be used to communicate with manyremote APs in the same sector.

[0114] The wireless hub bridges the trunk to the remote APs and thebackhaul line (e.g., T1 or T3) to the network's mobile switching center(MSC). The protocol stack in the wireless hub implements MAC and PHYlayers to the MSC on top of which is implemented an IP (InternetProtocol) layer on top of which is implemented a UDP layer (UniversalDatagram Protocal, in combination referred to as UDP/IP) for networkmanagement on top of which is implemented an XTunnel protocol. TheXTunnel protocol is a new format that includes aspects of mobility (e.g.as in mobile IP) and aspects of the Level 2 Tunnel Protocol (L2TP). TheXTunnel protocol is used to communicate from the wireless hub to the MSCand between inter-working functions (IWFs) in different networks or thesame network.

[0115] In FIG. 10, the protocol stack for the relay function in the basestation for supporting remote access points is shown. The relay functionincludes an interface to the backhaul line (depicted as the wirelesshub) and an interface to the remote AP (depicted as a trunk AP). Fromthe point of view of the wireless hub, the trunk AP (depicted in FIGS. 7and 10) actually behaves like the AP depicted in FIG. 7. Preferably, thebase station protocol stacks are split up into a wireless hub and atrunk AP with an Ethernet in between. In an N-sector wireless trunk,there are N wireless trunk APs in the cell site and one wireless hub.

[0116] In FIG. 11, the base station protocol stack for a cellarchitecture using a local AP is shown. The relay function includes aninterface to the backhaul line (depicted as the wireless hub) and an airlink interface to the end system (depicted as an AP). From the point ofview of the wireless hub, the AP (depicted in FIGS. 8 and 11) actuallybehaves like the trunk AP depicted in FIG. 8. Preferably, the basestation protocol stacks are split up into a wireless hub and a trunk APwith an Ethernet in between. In a N-sector cell, there are N accesspoints and a single wireless hub.

[0117] The backhaul network from the base station to the MSC has thefollowing attributes.

[0118] 1. The network is capable of routing IP datagrams between thebase station and the MSC.

[0119] 2. The network is secure. It is not a public internet. Trafficfrom trusted nodes only are allowed onto the network since the networkwill be used for not only transporting end system traffic, but also fortransporting authentication, accounting, registration and managementtraffic.

[0120] 3. The network has the necessary performance characteristics.

[0121] In typical application, the service provider is responsible forinstalling and maintaining the backhaul network on which the equipmentis installed.

[0122] The base stations supports the following backhaul interfaces forcommunicating with the MSC.

[0123] 1. Base stations support IP over PPP with HDLC links using pointto point T1 or fractional T3 links.

[0124] 2. Base stations support IP over frame relay using T1 orfractional T3 links.

[0125] 3. Base stations support IP over AAL5/ATM using T1 or fractionalT3 links.

[0126] 4. Base stations support IP over Ethernet links.

[0127] Since all of the above interfaces are based on IETF standardencapsulations, commercial routers may be used in the MSC to terminatethe physical links of the backhaul network. Higher layers are passed onand processed by the various servers and other processors.

[0128] End system registration procedures above the MAC layer aresupported. In the following, end system registration procedures at theMAC layer are ignored except where they impact the layers above.

[0129] End systems may register for service on their home network orfrom a foreign network. In both scenarios, the end system uses a foreignagent (FA) in the base station to discover a point of attachment to thenetwork and to register. In the former case, the FA is in the endsystem's home network. In the latter case, the FA is in a foreignnetwork. In either case, the network uses an IWF in the end system'shome network as an anchor point (i.e., unchanging throughout the sessionin spite of mobility). PPP frames to and from the end system travel viathe FA in the base station to the IWF in the home network. If the endsystem is at home, the home IWF is directly connected by means of thextunnel protocol to the base station. Note that the home IWF may becombined with the base station in the same node If the end system isroaming, a serving IWF in the foreign network is connected to the homeIWF over an I-interface. The serving IWF relays frames between the basestation and the home IWF. Note that the home IWF may be combined withthe base station in the same node. From the home IWF, data is sent to aPPP server which may reside in the same IWF or to a separate serverusing the L2TP protocol. The separate server may be owned and operatedby a private network operator (e.g. ISP or corporate intranet) who isdifferent from the wireless service provider. For the duration of thesession, the location of the home IWF and the PPP server remains fixed.If the end system moves while connected, it will have to re-registerwith a new foreign agent. However, the same home IWF and PPP servercontinues to be used. A new xtunnel is created between the new FA andthe IWF and the old xtunnel between the old foreign agent and the IWF isdestroyed.

[0130]FIG. 12 shows this network configuration for two end systems A andB, both of whose home wireless network is wireless service provider A(WSP-A). One end system is registered from the home wireless network andthe other from a foreign wireless network. The home IWF in WSP-A servesas the anchor point for both end systems. For both end systems, data isrelayed to the home IWF. The home IWF connects to an internet serviceprovider's PPP server owned by ISP-A. Here it is assumed that both endsystems have subscribed to the same ISP. If that were not the case, thenthe home IWF would be shown also connected to another ISP.

[0131] Within a wireless service providers network, data between basestations and the IWF is carried using the xtunnel protocol. Data betweenthe IWF and the PPP server is carried using Level 2 Tunneling Protocol(L2TP). Data between the serving IWF and the home IWF is carried usingthe I-xtunnel protocol.

[0132] In a simple scenerio, for a user in their home network requiringfixed service, the home IWF function may be dynamically activated in thebase station. Also, the serving IWF function may be activated for aroaming user in the base station.

[0133] Always using an IWF in the home network has its advantages anddisadvantages. An obvious advantage is simplicity. A disadvantage isthat of always having to relay data to and from a possibly remote homeIWF. The alternative is to send all the necessary information to theserving IWF so that it may connect to the end system's ISP/intranet andfor the serving IWF to send accounting information in near real timeback to the accounting server in the home network. This functionality ismore complex to implement, but more efficient because it reduces theneed to relay data over potentially long distances from the foreignnetwork to the home network.

[0134] For example, consider a case of a user who roams from Chicago toHong Kong. If the user's home network is in Chicago and the userregisters using a wireless service provider in Hong Kong, then in thefirst configuration, the anchor point will be the home IWF in Chicagoand all data will have to be relayed from Hong Kong to Chicago and viceversa. The home IWF in Chicago will connect to the user's ISP inChicago. With the second configuration, the end system user will beassigned an ISP in Hong Kong. Thus, data will not always have to berelayed back and forth between Chicago and Hong Kong. In the secondconfiguration, the serving IWF will serve as the anchor and never changefor the duration of the session even if the end system moves. However,the location of the FA may change as a result of end system movement inHong Kong.

[0135]FIG. 13 shows the second network configuration. In this figure,the home network for end system A and B is WSP-A. End system A registersfrom its home network, using its home IWF as an anchor point, and alsoconnects to its ISP-A using the ISPs PPP server. End system B registersfrom the foreign network of WSP-B and uses a serving IWF which serves asthe anchor point and connects the end system to an ISP using the ISP'sPPP server. In this configuration, data for end system B does not haveto be relayed from the foreign network to the home network and viceversa.

[0136] In order for this configuration to work, not only must there beroaming agreements between the home and the foreign wireless serviceproviders, but there also must be agreements between the foreignwireless service provider and the end system's internet service providerdirectly or through an intermediary. In the example above, not only mustthe wireless service provider in Hong Kong have a business agreementwith the wireless service provider in Chicago, but the WSP in Hong Kongmust have a business agreement with the user's Chicago ISP and access tothe Chicago ISPs PPP server in Hong Kong or a business agreement withanother ISP locally in Hong Kong who has a business agreement forroaming with the user's Chicago ISP. Additionally, the WSP in Hong Kongmust be able to discover these roaming relationships dynamically inorder to do user authentication and accounting and to set up theappropriate tunnels.

[0137] It is difficult for those companies who are in the Internetinfrastructure business to work out suitable standards in the IETF forall of these scenarios. Thus, a preferable embodiment for the presentsystems to implement the simpler, potentially less efficientconfiguration, where the IWF in the home network is always used as theanchor point. However, in the presence of suitable industrystandardization of protocols for Internet roaming, the secondconfiguration should be regarded as equivalent or alternativeembodiment.

[0138] An end system will have to register with the wireless networkbefore it can start PPP and send and receive data. The end system firstgoes through the FA discovery and registration phases. These phasesauthenticate and register the end system to the wireless serviceprovider. Once these phases are over, the end system starts PPP. Thisincludes the PPP link establishment phase, the PPP authentication phaseand the PPP network control protocol phase. Once these phases are over,the end system is able to send and receive IP packets using PPP.

[0139] The following discussion assumes that the end system is roamingand registering from a foreign network. During the FA discovery phase,the end system (through its user registration agent) waits for orsolicits an advertisement from the foreign agent. The user registrationagent uses advertisement messages sent by a near by foreign agent todiscover the identity of the FA and to register. During this phase, theuser registration agent of the end system selects a FA and issues aregistration request to it. The FA acting as a proxy registration agentforwards the registration request to its registration server (theregistration server in the foreign WSP). The registration server usesUser-Name from the user registration agent's request to determine theend system's home network, and forwards the registration request forauthentication to a registration server in the home network. Uponreceiving the registration request relayed by the foreign registrationserver, the home registration server authenticates the identity of theforeign registration server and also authenticates the identity of theend system. If authentication and registration succeeds, the homeregistration server selects an IWF in the home network to create anI-xtunnel link between the home IWF and the serving IWF (in the foreignWSP). The IWF in the home network serves as the anchor point for theduration of the PPP session.

[0140] Once the authentication and registration phases are over, thevarious PPP phases will be started. At the start of PPP, an L2TPconnection is created between the home IWF and requested ISP/intranetPPP server. In the PPP authentication phase, PPP passwords usingPassword Authentication Protocol (PAP) or Challenge AuthenticationProtocol CHAP are exchanged and the ISP or intranet PPP serverindependently authenticates the identity of the end system.

[0141] Once this succeeds, the PPP network control phase is started. Inthis phase, an IP address is negotiated and assigned to the end systemby the PPP server and the use of TCP/IP header compression is alsonegotiated. When this is complete, the end system is able to send andreceive IP packets using PPP to its ISP or a corporate intranet.

[0142] Note that two levels of authentication are performed. The firstauthentication authenticates the identity of the end system to theregistration server in the home network and the identities of theforeign network and the home network to each other. To perform thisfunction, the foreign agent forwards the end system's registrationrequest using, for example, an IETF Radius protocol to a registrationserver in its local MSC in a Radius Access-Request packet Using the endsystem's domain name, the foreign registration server determines theidentity of the end system's home network and home registration server,and acting as a Radius proxy, encapsulates and forwards the request tothe end system's home registration server. If the foreign registrationserver cannot determine the identity of the end system's home, it mayoptionally forward the Radius request to a registration server that actslike a broker (e.g. one that is owned by a consortium of wirelessservice providers), which can in turn proxy the Radius Access-Request tothe final home registration server. If the local registration server isunable to service the registration request locally or by proxying, thenit rejects the foreign agent's registration request and the foreignagent rejects the end system's registration request. Upon receiving theRadius Access-Request, the home registration server performs thenecessary authentication of the identities of the foreign network andthe end system. If authentication and registration succeeds, the homeregistration server responds with a Radius Access-Response packet to theforeign registration server which sends a response to the foreign agentso that a round trip can be completed. The registration request isrejected if the home registration server is unable to comply for anyreason.

[0143] The second level of authentication verifies the identity of theend system to the intranet or ISP PPP server. PPP authentication,separate from mobility authentication allows the infrastructureequipment to be deployed and owned separately from the ISP.

[0144]FIG. 14 is a ladder diagram showing the registration sequence fora roaming end system. It is assumed that the PPP server and the home IWFare in the same server and L2TP is not required. Note the interactionswith accounting servers to start accounting on behalf of the registeringend system and also directory servers to determine the identity of thehome registration server and to authenticate the end system's identity.More information on accounting, billing, roaming (between serviceproviders) and settlement will be provided below.

[0145] MAC layer messages from the user registration agent of the endsystem may be used to initiate Agent Solicitation. The MAC layermessages are not shown for clarity.

[0146] In FIG. 14, the end system (mobile) initially solicits anadvertisement and the foreign agent replies with an advertisement thatprovides the end system with information about the network to which theforeign agent belongs including a care-of-address of the foreign agent.Alternatively, this phase may be removed and all network advertisementsmay be done by a continuously emitted MAC layer beacon message. In thiscase, the network is assumed to be a foreign wireless service provider.Then, a user registration agent (in the end system) incorporates theinformation about the foreign agent (including the user name and othersecurity credentials) and its network into a request and sends therequest to the foreign agent. The foreign agent, as a proxy registrationagent, relays the request to the foreign registration server (i.e., theregistration server for the foreign wireless service provider. Then, theforeign registration server, recognizing that it is not the homedirectory, accesses the foreign directory server with the FDD in theforeign wireless service provider to learn how to direct theregistration request to the home registration server of the wirelessservice provider to which the end system belongs. The foreignregistration server responds with the necessary forwarding information.Then, the foreign registration server encapsulates the end system'sregistration request in a Radius access request and relays theencapsulated request to the home registration server of the wirelessservice provider to which the end system belongs. The home registrationserver accesses the home directory server with the HDD of the homeregistration server to learn at least authentication information aboutthe foreign service provider. Optionally, the home registration serveraccesses the subscriber's directory to learn detail subscriber serviceprofile information (e.g., quality of service options subscribed to,etc.). When all parties are authenticated, the home registration serversends a start IWF request to the home IWF and PPP server. The home IWFand PPP server starts the home accounting server and then sends a startIWF response to the home registration server. The home registrationserver then sends a Radius access response to the foreign registrationserver. The foreign registration server then sends a start IWF requestto the serving IWF server. The serving IWF server starts the servingaccounting server and then sends a start IWF response to the foreignregistration server. The foreign registration server sends aregistration reply to the foreign agent, and the foreign agent relaysthe registration reply to the end system.

[0147] A link control protocol (LCP) configuration request is send bythe end system through the foreign registration server to the home IWFand PPP server. The home IWF and PPP server sends an LCP configurationacknowledgment through the foreign registration server to the endsystem.

[0148] Similarly, a password authentication protocol (PAP)authentication request is sent to and acknowledged by the home IWF andPPP server. Alternatively, a challenge authentication protocol (CHAP)may be used to authenticate. Both protocols may be used to authenticateor this phase may be skipped.

[0149] Similarly, an IP configuration protocol (IPCP) configure requestis sent to and acknowledged by the home IWF and PPP server.

[0150] The connection to the end system may be terminated because of anyone of the following reasons.

[0151] 1. User initiated termination. Under this scenario, the endsystem first terminates the PPP gracefully. This includes terminatingthe PPP network control protocol (IPCP) followed by terminating the PPPlink protocol. Once this is done, the end system de-registers from thenetwork followed by termination of the radio link to the access point.

[0152] 2. Loss of wireless link. This scenario is detected by the modemand reported to the modem driver in the end system. The upper layers ofthe software are notified to terminate the stacks and notify the user.

[0153] 3. Loss of connection to the foreign agent. This scenario isdetected by the mobility driver in the end system. After trying tore-establish contact with a (potentially new) foreign agent and failing,the driver sends an appropriate notification up the protocol stack andalso signals the modem hardware below to terminate the wireless link.

[0154] 4. Loss of connection to the IWF. This is substantially the sameas for loss of connection to the foreign agent.

[0155] 5 Termination of PPP by IWF or PPP server. This scenario isdetected by the PPP software in the end system. The end system's PPPdriver is notified of this event. It initiates de-registration from thenetwork followed by termination of the wireless link to the accesspoint.

[0156] End system service configuration refers to the concept ofconfiguring the network service for an end system based on thesubscriber's service profile. The subscriber's service profile is storedin a subscriber directory The service profile contains information toenable the software to customize wireless data service on behalf of thesubscriber. This includes information to authenticate the end system,allow the end system to roam and set up connections to the end system'sinternet service provider. Preferably, this information also includesother parameters, like, quality of service. In addition to thesubscriber directory, a home domain directory (HDD) and a foreign domaindirectory (FDD) are used for roaming and for authenticating the foreignand home registration servers to each other. The HDD stores informationabout the end system's home network and the FDD stores information aboutforeign networks that a subscriber may visit.

[0157]FIG. 15 shows how these directories map into the networkarchitecture and are used during registration for an end system that isregistering at home. In step 0 the end system (mobile) solicits andreceives an advertisement from the foreign agent to provides the endsystem with information about the network to which the foreign agentbelongs. In this case, the network is the home wireless serviceprovider. In step 1, user registration agent (in the end system)incorporates the information about the foreign agent and its network andits security credentials into a request and sends the request to theforeign agent. In step 2, the foreign agent, as a proxy registrationagent, relays the request to the home registration server. In step 3,the home registration server accesses the HDD of the home wirelessservice provider to learn at least authentication information. In step4, the home registration server accesses the subscriber directory tolearn detail subscriber service profile information (e.g., quality ofservice options subscribed to, etc.). In step 5, the home registrationserver notifies the foreign agent of the access response. In steps 6 and7, the foreign agent notifies the end system (i.e., mobile) of theregistration reply.

[0158]FIG. 16 shows directory usage for an end system that isregistering from a foreign network. In step 0 the end system (mobile)solicits and receives an advertisement and the foreign agent advertiseswhich provides the end system with information about the network towhich the foreign agent belongs. In this case, the network is a foreignwireless service provider. In step 1, user registration agent (in theend system) incorporates the information about the foreign agent and itsnetwork and its security credential into a request and sends the requestto the foreign agent. In step 2, the foreign agent, as a proxyregistration agent, relays the request to the foreign registrationserver (i.e., the registration server for the foreign wireless serviceprovider. In step 3, the foreign registration server accesses the HDD offoreign wireless service provider to learn the network to which the endsystem belongs. In step 4, the foreign registration server forwards theend system's request to the home registration server of the end system'shome wireless service provider. In step 5, the home registration serveraccesses the FDD of the home registration server to learn at leastauthentication information about the foreign service provider. In step6, the home registration server accesses the subscriber's directory tolearn detail subscriber service profile information (e.g., quality ofservice options subscribed to, etc.). In step 7, the home registrationserver notifies the foreign registration server of the access response.In step 8, the foreign registration server forwards to the foreign agentthe access response. In step 9, the foreign agent notifies the endsystem (i.e., mobile) of the registration reply.

[0159] Protocol handling scenarios handle bearer data and the associatedstacks for transporting bearer data to and from an end system. Theprotocol stacks for the cell architectures use local APs (FIG. 17) andremote APs (FIG. 18).

[0160]FIG. 17 shows the protocol stacks for handling communicationsbetween an end system (in its home network) and a home IWF for EndSystem@Home. FIG. 17 shows the protocol handling for a cell architecturewhere the access point and the wireless hub are co-located.

[0161]FIG. 18 shows the protocol handling for a cell architecture wherethe access point is located remotely from the wireless hub. As shown,PPP terminates in the IWF and the configuration provides direct internetaccess. The configuration for the case where the PPP server is separatefrom the IWF is described later.

[0162] In FIG. 18, PPP frames from the end system are encapsulated inRLP (radio link protocol) frames which are encapsulated at the remoteaccess point in MAC frames for communicating with the trunk access point(i.e., an access point physically located near the wireless hub), theremote access point being coupled to the access point by, for example, awireless trunk). The access point functions as a MAC layer bridge andrelays frames from the air link to the foreign agent in the wirelesshub. The foreign agent de-encapsulates the RLP frames out of the MACframes, and using the xtunnel protocol, relays the RLP frames to theIWF. A similar, albeit reverse, process occurs for transmitting framesfrom the IWF to the end system.

[0163] If the end system moves to another foreign agent, then a newxtunnel will be automatically created between the new foreign agent andthe IWF, so that PPP traffic continues to flow between them, withoutinterruption.

[0164] In the remote AP cell architecture (FIG. 18) using wirelesstrunks between the remote AP and the trunk AP, the air link between theend system and the access point may operate at a different frequency(f1) and use a different radio technology as compared to the frequency(f2) and radio technology of the trunk.

[0165]FIG. 19 shows the protocol stacks for a roaming end system. Theserving IWF uses of the I-xtunnel protocol between the serving IWF andhome IWF. The rest of the protocol stacks remain unchanged and are notshown. This architecture may be simplified by merging the serving IWFinto the base station, thus eliminating the XWD protocol.

[0166] The RLP layer uses sequence numbers to drop duplicate PPPdatagrams and provide in-sequence delivery of PPP datagrams between theend system and the IWF. It also provides a configurable keep-alivemechanism to monitor link connectivity between the end system and theIWF. Additionally, in an alternative embodiment, the RLP layer alsoprovides re-transmission and flow control services in order to reducethe overall bit error rate of the link between the end system and theIWF. The RLP between the end system and the IWF is started at thebeginning of the session and remains active throughout the session andeven across hand-offs.

[0167] In contrast to the specification in the mobile IP RFC (RFC 2003),IP in IP encapsulation is not used for tunneling between the foreignagent and the home IWF. Instead a new tunneling protocol, implemented ontop of UDP is used. This tunneling protocol is a simplified version ofthe L2TP protocol. The reasons for this choice are as follows.

[0168] 1. The encapsulation protocol specified in RFC 2003 does notprovide flow control or in-sequence delivery of packets. The presentlydescribed network may need these services in the tunnel over thebackhaul. Flow control may be needed to reduce the amount ofretransmissions over the air link because of packet loss due to flowcontrol problems over the network between the base station and the MSCor because of flow control problems in the base station or the IWF.

[0169] 2. By using a UDP based tunneling protocol, the implementationcan be done at the user level and then put into the kernel forperformance reasons, after it has been debugged.

[0170] 3. Using RFC 2003, there is no easy way of creating tunnelstaking into account quality of service and load balancing. In order totake QOS into account, it should be possible to set up tunnels overlinks that already provide the required QOS. Secondly, using RFC 2003,there is no easy way to provide load balancing to distribute bearertraffic load over multiple links between the base station and the MSC.

[0171] 4. In order to implement IP in IP encapsulation as specified inRFC 2003, developers require access to IP source code. In commercialoperating systems, source code for the TCP/IP stack is generallyproprietary to other equipment manufacturers. Purchasing the TCP/IPstack from a vendor and making changes to the IP layer to support mobileIP tunneling would require a developer to continue supporting a variantversion of the TCP/IP stack. This adds cost and risk.

[0172] While it is noted that the tunneling protocol between the basestation and the IWF is non-standard and that the wireless serviceprovider will not be able to mix and match equipment from differentvendors, the use of a non-standard tunneling protocol within a singlewireless service provider network is transparent to end systems andequipment from other vendors.

[0173] The new tunneling protocol is based on L2TP. By itself, L2TP is aheavyweight tunneling protocol so that L2TP has a lot of overheadassociated with tunnel creation and authentication. The new tunnelingprotocol of the present system has less overhead. The new xtunnelprotocol has the following features.

[0174] 1. The xtunnel creation adds vendor specific extensions to RadiusAccess Request and Radius Access Response messages between the basestation and the registration server. These extensions negotiate tunnelparameters and to create the tunnel.

[0175] 2. The registration server is able to delegate the actual work oftunneling and relaying packets to a different IP address, and therefore,to a different server in the MSC. This permits the registration serverto do load balancing across multiple IWF servers and to providedifferent QOS to various users.

[0176] 3. The xtunnel protocol supports in-band control messages fortunnel management. These messages include echo request/response to testtunnel connectivity, disconnect request/response/notify to disconnectthe tunnel and error notify for error notifications. These messages aresent over the tunneling media, for example, UDP/IP.

[0177] 4. The xtunnel protocol sends payload data over the tunnelingmedia, for example, UDP/IP. The xtunnel protocol supports flow controland in-sequence packet delivery.

[0178] 5. The xtunnel protocol may be implemented over media other thanUDP/IP for quality of service.

[0179] The network supports direct internet connectivity by terminatingthe PPP in the home IWF and routing IP packets from the IWF to theinternet via a router using standard IP routing techniques. Preferably,the IWF runs Routing Information Process (RIP), and the router also runsRIP and possibly other routing protocols like Open Shortest Path First(OSPF).

[0180] The network supports a first configuration for a wireless serviceprovider who is also an internet service provider. In thisconfiguration, the home IWF in the MSC also functions as a PPP server.This IWF also runs internet routing protocols like RIP and uses a routerto connect to the internet service provider's backbone network.

[0181] The network supports a second configuration for a wirelessservice provider who wishes to allow end systems to connect to one ormore internet service providers, either because the WSP itself is notISPs, or because the WSP has agreements with other ISPs to provideaccess to end users. For example, a wireless service provider may electto offer network access to an end user and may have an agreement with a3^(rd) party ISP to allow the user who also has an account with the3^(rd) party ISP to access the ISP from the WSP network. In thisconfiguration, the PPP server does not run in the home IWF installed atthe MSC. Instead, a tunneling protocol like L2TP (Layer Two TunnelingProtocol) is used to tunnel back to the ISP's PPP server. FIG. 10 showsthe protocol stacks for this configuration for an end system that is athome.

[0182] The location of the home IWF and the ISP PPP server remains fixedthroughout the PPP session. Also, the L2TP tunnel between the IWF andthe ISP's PPP server remains up throughout the PPP session. The physicallink between the IWF and the PPP server is via a router using adedicated T1 or T3 or frame relay or ATM network. The actual nature ofthe physical link is not important from the point of view of thearchitecture.

[0183] This configuration also supports intranet access. For intranetaccess, the PPP server resides in the corporate intranet and the homeIWF uses L2TP to tunnel to it.

[0184] For a fixed end system, the protocol handling for intranet or ISPaccess is as shown in FIG. 20 with the difference that the roaming endsystem uses a serving IWF to connect to its home IWF. The protocolhandling between a serving IWF and a home IWF has been describedearlier. In FIG. 20, the home IWF may be merged into the wireless hubeliminating the X-Tunnel protocol. Also, the serving IWF may be mergedinto the wireless hub, thus eliminating the X-Tunnel protocol.

[0185]FIG. 21 shows the protocol stacks used during the registrationphase (end system registration) for a local AP cell architecture. Thestack for a remote AP cell architecture is very similar.

[0186] The scenario shown above is for a roaming end system. For an endsystem at home, there is no foreign registration server in theregistration path.

[0187] Note the mobility agent in the end system. The mobility agent inthe end system and foreign agent in the wireless hub are conceptuallysimilar to the mobile IP RFC 2002. The mobility agent handles networkerrors using time-outs and re-trys. Unlike the known protocol stacks forbearer data, RLP is not used. The foreign agent and the registrationservers use Radius over UDP/IP to communicate with each other forregistering the end system.

[0188] Several aspects of security must be considered. The first,authenticating the identities of the end system and the foreign/homenetworks during the wireless registration phase. Second, authenticatingthe identity of the end system with its PPP server during the PPPauthentication phase. Third, authentication for storing accounting data,for billing and for updating home domain information. Fourth, encryptionof bearer traffic transmitted to and from the end system. Fifth,encryption for exchanging billing information across service providerboundaries.

[0189] Shared secrets are used to authenticate the identity of endsystems with their home networks and the identity of the home andforeign networks with each other during wireless registration.

[0190] End system authentication uses a 128-bit shared secret to createan authenticator for its registration request. The authenticator iscreated using the known MD5 message digest algorithm as described in themobile IP RFC 2002. Alternatively, a different algorithm may be used.The shared secret is not sent in the registration request by the endsystem. Only the authenticator is sent. On receiving the registrationrequest from the end system, the home registration server re-computesthe authenticator over the registration request data using the sharedsecret. If the computed authenticator value matches the authenticatorvalue sent by the end system, the home registration server allows theregistration process to proceed. If the values do not match, the homeregistration server logs the event, generates a security violation alarmand a nak (i.e., a negative acknowledgment) to the request.

[0191] In the registration reply, the home registration server does thesame—that is to say, uses the shared secret to create an authenticatorfor the registration reply that it sends to the end system. Uponreceiving the reply, the end system re-computes the authenticator usingthe shared secret. If the computed value does not match theauthenticator value sent by the home registration server in the reply,the end system discards the reply and tries again.

[0192] These network security concepts are similar to the conceptsdefined in mobile IP RFC 2002. According to the RFC, a mobility securityassociation exist between each end system and its home network. Eachmobility security association defines a collection of security contexts.Each security context defines an authentication algorithm, a mode, asecret (shared or public-private), style of replay protection and thetype of encryption to use. In the context of the present network, theend system's User-Name (in lieu of the mobile IP home address) is usedto identify the mobility security association between the end system andits home network. Another parameter, called the security parameter index(SPI), is used to select a security context within the mobility securityassociation. In a basic embodiment of the invention, only the defaultmobile IP authentication algorithm (keyed-MD5) and the default mode(“prefix+suffix”) are supported with 128-bit shared secrets. Networkusers are allowed to define multiple shared secrets with their homenetworks. The mechanism for creating security contexts for end users,assigning an SPI to each security context and for setting the contentsof the security context (which includes the shared secret) and formodifying their contents are described below. During registration, a128-bit message digest is computed by the end system in prefix+suffixmode using the MD5 algorithm. The shared secret is used as the prefixand the suffix for the data to be protected in the registration request.The authenticator thus computed, along with the SPI and the User-Nameare transmitted in the registration request by the end system. Uponreceiving the end system's registration request, the foreignregistration server relays the request along with the authenticator andthe SPI, unchanged to the home registration server. Upon receiving theregistration request directly from the end system or indirectly via aforeign registration server, the home registration server uses the SPIand the User-Name to select the security context. The home serverre-computes the authenticator using the shared secret. If the computedauthenticator value matches the value of the authenticator sent in therequest by the end system, the user's identity will have beensuccessfully authenticated. Otherwise, the home registration server naks(negatively acknowledges) the registration request sent by the endsystem.

[0193] The registration reply sent by the home registration server tothe end system is also authenticated using the algorithm describedabove. The SPI and the computed authenticator value is transmitted inthe registration reply message by the home server to the end system.Upon receiving the reply, the end system re-computes the authenticator,and if the computed value does not match the transmitted value, it willdiscard the reply and retry.

[0194] The user's end system has to be configured with the shared secretand SPIs for all security contexts that the user shares with itsregistration server(s) This configuration information is preferablystored in a Win 95 registry for Windows 95 based end systems. Duringregistration, this information is accessed and used for authenticationpurposes.

[0195] In the network, Radius protocols are used by foreign agent FA toregister the end system and to configure the xtunnel between thewireless hub and the home and serving IWFs on behalf of the end system.On receiving a registration request from the end system, the FA createsa Radius Access-Request packet, stores its own attributes into thepacket, copies the end system's registration request attributesunchanged into this packet and sends the combined request to theregistration server in the MSC.

[0196] Radius authentication requires that the Radius client (in thiscase, the FA in the base station) and the Radius server (in this case,the registration server in the MSC) share a secret for authenticationpurposes. This shared secret is also used to encrypt any privateinformation communicated between the Radius client and the Radiusserver. The shared secret is a configurable parameter. The networkfollows the recommendations in the Radius RFC and uses the shared secretand the MD5 algorithm for authentication and for encryption, whereencryption is needed. The Radius-Access Request packet sent by the FAcontains a Radius User-Name attribute (which is provided by the endsystem) and a Radius User-Password attribute. The value of theUser-Password attribute is also a configurable value and encrypted inthe way recommended by the Radius protocol. Other network specificattributes, which are non-standard attributes from the point of view ofthe Radius RFC standards, are encoded as vendor specific Radiusattributes and sent in the Access-Request packet.

[0197] The following attributes are sent by the FA to its registrationserver in the Radius Access-Request packet.

[0198] 1. User-Name Attribute. This is the end system's user-name assupplied by the end system in its registration request.

[0199] 2. User-Password Attribute. This user password is supplied by thebase station/wireless hub on behalf of the user. It is encoded asdescribed in the Radius EFC using the secret shared between the basestation and its registration server.

[0200] 3. NAS-Port. This is the port on the base station.

[0201] 4. NAS-IP-Address. This is the IP address of the base station.

[0202] 5. Service-Type. This is framed service.

[0203] 6. Framed Protocol. This is a PPP protocol.

[0204] 7. Xtunnel Protocol Parameters. These parameters are sent by thebase station to specify the parameters necessary to set up the xtunnelprotocol on behalf of the end system. This is a vendor-specificattribute.

[0205] 8. AP-IP-Address. This is the IP address of the AP through whichthe user is registering. This is a vendor-specific attribute.

[0206] 9. AP-MAC-Address. This is the MAC address of the AP throughwhich the user is registering. This is a vendor-specific attribute.

[0207] 10. End system's Registration Request. The registration requestfrom the end system is copied unchanged into this vendor specificattribute.

[0208] The following attributes are sent to the FA from the registrationserver in the Radius Access-Response packet.

[0209] 1. Service Type. This is a framed service.

[0210] 2. Framed-Protocol. This is a PPP.

[0211] 3. Xtunnel Protocol Parameters. These parameters are sent by theregistration server to specify the parameters necessary to set up thextunnel protocol on behalf of the end system. This is a vendor-specificattribute.

[0212] 4. Home Registration Server's Registration Reply. This attributeis sent to the FA from the home registration server. The FA relays thisattribute unchanged to the end system in a registration reply packet. Ifthere is a foreign registration server in the path, this attribute isrelayed by it to the FA unchanged. It is coded as a vendor-specificattribute.

[0213] To provide service to roaming end systems, the foreign networkand the home network are authenticated to each other for accounting andbilling purposes using the Radius protocol for authentication andconfiguration. This authentication is performed at the time of endsystem registration. As described earlier, when the registration serverin the foreign network receives a registration request from an endsystem (encapsulated as a vendor specific attribute in a Radius-AccessRequest packet by the FA), it uses the end system's User-Name todetermine the identity of the end system's home registration server byconsulting its home domain directory HDD. The following information isstored in home domain directory HDD and accessed by the foreignregistration server in order to forward the end system's registrationrequest.

[0214] 1. Home Registration Server IP Address. This is the IP address ofthe home registration server to forward the registration request.

[0215] 2. Foreign Registration Server Machine Id. This is the machine IDof the foreign registration server in SMTP (simplified mail transferprotocol) format (e.g., machine@fqdn where machine is the name of theforeign registration server machine and fqdn is the fully qualifieddomain name of the foreign registration server's domain).

[0216] 3. Tunneling Protocol Parameters. These are parameters forconfiguring the tunnel between the serving IWF and the home IWF onbehalf of the end system. These include the tunneling protocol to beused between them and the parameters for configuring the tunnel.

[0217] 4. Shared Secret. This is the shared secret to be used forauthentication between the foreign registration server and the homeregistration server. This secret is used for computing the RadiusUser-Password attribute in the Radius packet sent by the foreignregistration server to the home registration server. It is definedbetween the two wireless service providers.

[0218] 5. User-Password. This is the user password to be used on behalfof the roaming end system. This user password is defined between the twowireless service providers. This password is encrypted using the sharedsecret as described in the Radius RFC.

[0219] 6. Accounting Parameters. These are parameters for configuringaccounting on behalf of the end system that is registering. Theseparameters are sent by the registration server to its IWF forconfiguring accounting on behalf of the end system.

[0220] Using this information, the foreign registration server creates aRadius Access-Request, adds its own registration and authenticationinformation into the Radius Access-Request, copies the registrationinformation sent by the end system unchanged into the RadiusAccess-Request and sends the combined request to the home registrationserver.

[0221] Upon receiving the Radius-Access Request from the foreignregistration server (for a roaming end system) or directly from the FA(for an end system at home), the home registration server consults itsown directory server for the shared secrets to verify the identity ofthe end system and the identity of the foreign registration server in aroaming scenario by re-computing authenticators.

[0222] After processing the request successfully, the home registrationserver creates a Radius Access-Accept response packet and sends it tothe foreign registration server if the end system is roaming, ordirectly to the FA from which it received the Radius Access-Request. Theresponse contains the registration reply attribute that the FA relays tothe end system.

[0223] If the request can not be processed successfully, the homeregistration server creates a Radius Access-Reject response packet andsends it to the foreign registration server if the end system isroaming, or directly to the FA from which it received the RadiusAccess-Request. The response contains the registration reply attributethat the FA will relays to the end system.

[0224] In a roaming scenario, the response from the home registrationserver is received by the foreign registration server. It isauthenticated by the foreign registration server using the sharedsecret. After authenticating, the foreign registration server processesthe response, and in turn, it generates a Radius response packet (Acceptor Reject) to send to the FA. The foreign registration server copies theregistration reply attribute from the home registration server's Radiusresponse packet, unchanged, into its Radius response packet.

[0225] When the FA receives the Radius Access-Response or RadiusAccess-Reject response packet, it creates a registration reply packetusing the registration reply attributes from the Radius response, andsends the reply to the end system, thus completing the round tripregistration sequence.

[0226] Mobile IP standards specifies that replay protection forregistrations are implemented using time stamps, or optionally, usingnonces. However, since replay protection using time stamps requiresadequately synchronized time-of-day clocks between the correspondingnodes, the present system implements replay protection duringregistration using nonces even though replay protection using timestamps is mandatory in the Mobile IP standards and the use nonces isoptional. However, replay protection using time stamps as an alternativeembodiment is envisioned.

[0227] The style of replay protection used between nodes is stored inthe security context in addition to the authentication context, mode,secret and type of encryption.

[0228] The network supports the use of PPP PAP (password authentication)and CHAP (challenge authenticated password) between the end system andits PPP server. This is done independently of the registration andauthentication mechanisms described earlier. This allows a privateintranet or an ISP to independently verify the identity of the user.

[0229] Authentication for accounting and directory services is describedbelow with respect to accounting security. Access to directory serversfrom network equipment in the same MSC need not be authenticated.

[0230] The network supports encryption of bearer data sent between theend system and the home IWF. End systems negotiate encryption to be onor off by selecting the appropriate security context. Upon receiving theregistration request, the home registration server grants the endsystem's request for encryption based upon the security context. Inaddition to storing the authentication algorithm, mode, shared secretand style of replay protection, the security context is also used tospecify the style of encryption algorithm to use. If encryption isnegotiated between the end system and the home agent, then the completePPP frame is so encrypted before encapsulation in RLP.

[0231] The IWF, the accounting server and the billing system are part ofthe same trusted domain in the MSC. These entities are either connectedon the same LAN or part of a trusted intranet owned and operated by thewireless service provider. Transfer of accounting statistics between theIWF and the accounting server and between the accounting server and thecustomer's billing system may be encrypted using Internet IP securityprotocols like IP-Sec.

[0232] The network makes it more difficult to monitor the location ofthe end system because it appears that all PPP frames going to and fromthe end system go through the home IWF regardless of the actual locationof the end system device.

[0233] Accounting data is collected by the serving IWF and the home IWFin the network. Accounting data collected by the serving IWF is sent toan accounting server in the serving IWF's MSC. Accounting data collectedby the home IWF is sent to an accounting server in the home IWF's MSC.The accounting data collected by the serving IWF is used by the foreignwireless service provider for auditing and for settlement of billsacross wireless service provider boundaries (to support roaming andmobility). The accounting data collected by the home IWF is used forbilling the end user and also for settlement across wireless serviceprovider boundaries to handle roaming and mobility.

[0234] Since all data traffic flows through the home IWF, regardless ofthe end system's location and the foreign agent's location, the home IWFhas all the information to generate bills for the customer and alsosettlement information for the use of foreign networks.

[0235] The serving IWF and the home IWF preferably use the Radiusaccounting protocol for sending accounting records for registered endsystems. The Radius accounting protocol is as documented in a draft IETFRFC. For the present invention, the protocol has to be extended byadding vendor specific attributes for the network and by addingcheck-pointing to the Radius Accounting protocol. Check-pointing in thiscontext refers to the periodic updating of accounting data to minimizerisk of loss of accounting records.

[0236] The Radius accounting protocol runs over UDP/IP and uses re-trysbased on acknowledgment and time outs. The Radius accounting client(serving IWFs or home IWFs) send UDP accounting request packets to theiraccounting servers which send acknowledgments back to the accountingclients.

[0237] In the network, the accounting clients (serving IWF and the homeIWF) emit an accounting start indication at the start of the user'ssession and an accounting stop indication at the end of the user'ssession. In the middle of the session, the accounting clients emitaccounting checkpoint indications. In contrast, the Radius accountingRFC does not specify an accounting checkpoint indication. The softwareof the present system creates a vendor specific accounting attribute forthis purpose. This accounting attribute is present in all RadiusAccounting-Request packets which have Acct-Status-Type of Start(accounting start indications). The value of this attribute is used toconvey to the accounting server whether the accounting record is acheck-pointing record or not. Check-pointing accounting reports have atime attribute and contain cumulative accounting data from the start ofthe session. The frequency of transmitting check-point packets isconfigurable in the present invention.

[0238] The serving IWF and the home IWF are configured by theirrespective registration servers for connecting to their accountingservers during the registration phase. The configurable accountingparameters include the IP address and UDP port of the accounting server,the frequency of check-pointing, the session/multi-session id and theshared secret to be used between the accounting client and theaccounting server.

[0239] The network records the following accounting attributes for eachregistered end system. These accounting attributes are reported inRadius accounting packets at the start of the session, at the end of thesession and in the middle (check-point) by accounting clients to theiraccounting servers.

[0240] 1. User Name. This is like the Radius User-Name attributediscussed above. This attribute is used to identify the user and ispresent in all accounting reports. The format is “user@domain” wheredomain is the fully qualified domain name of the user's home.

[0241] 2. NAS IP Address. This is like the Radius NAS-IP-Addressattribute discussed above. This attribute is used to identify the IPaddress of the machine running the home IWF or the serving IWF.

[0242] 3. Radio Port. This attribute identifies the radio port on theaccess point providing service to the user. This attribute is encoded asa vendor specific attribute.

[0243] 4. Access Point IP Address. This attribute identifies the IPaddress of the access point providing service to the user. Thisattribute is encoded as a vendor specific attribute.

[0244] 5. Service Type. This is like the Radius Service-Type attributedescribed above. The value of this attribute is Framed.

[0245] 6. Framed Protocol. This is like the Radius Framed-Protocolattribute described above. The value of this attribute is set toindicate PPP.

[0246] 7. Accounting Status Type. This is like the RadiusAcct-Status-Type attribute described above. The value of this attributemay be Start to mark the start of a user's session with the Radiusclient and Stop to mark the end of the user's session with the Radiusclient. For accounting clients, the Acct-Status-Type/Start attribute isgenerated when the end system registers. The Acct-Status-type/Stopattribute is generated when the end system de-registers for any reason.For checkpoints, the value of this attribute is also Start and theAccounting Checkpoint attribute is also present.

[0247] 8. Accounting Session Id. This is like the Radius Acct-Session-Iddescribed above. In a roaming scenario, this session id is assigned bythe foreign registration server when the end system issues aregistration request. It is communicated to the home registration serverby the foreign registration server during the registration sequence. Thehome network and the foreign network both know the Acct-Session-Idattribute and are able to emit this attribute while sending accountingrecords to their respective accounting servers. In a “endsystem-at-home” scenario, this attribute is generated by the homeregistration server. The registration server communicates the value ofthis attribute to the IWF which emits it in all accounting records.

[0248] 9. Accounting Multi-Session Id. This is like the RadiusAcct-Multi-Session-Id discussed above. This id is assigned by the homeregistration server when a registration request is received from a FAdirectly or via a foreign registration server on behalf of an endsystem. It is communicated to the foreign registration server by thehome registration server in the registration reply message. Theregistration server(s) communicates the value of this attribute to theIWF(s) which emit it in all accounting records.

[0249] With true mobility added to the architecture, the id is used torelate together the accounting records from different IWFs for the sameend system if the end system moves from one IWF to another. Forhand-offs across IWF boundaries, the Acct-Session-Id is different foraccounting records emanating from different IWFs. However, theAcct-Multi-Session-Id attribute is the same for accounting recordsemitted by all IWFs that have provided service to the user. Since thesession id and the multi-session id are known to both the foreignnetwork and the home network, they are able to emit these attributes inaccounting reports to their respective accounting servers. With thesession id and the multi-session id, billing systems are able tocorrelate accounting records across IWF boundaries in the same wirelessservice provider and even across wireless service provider boundaries.

[0250] 1. Accounting Delay Time. See Radius Acct-Delay-Time attribute.

[0251] 2. Accounting Input Octets. See Radius Acct-Input-Octets. Thisattribute is used to keep track of the number of octets sent by the endsystem (input to the network from the end system). This count is used totrack the PPP frames only. The air link overhead, or any overheadimposed by RLP, etc. is not counted.

[0252] 3. Accounting Output Octets. See Radius Acct-Output-Octets. Thisattribute is used to keep track of the number of octets sent to the endsystem (output from the network to the end system). This count is usedto track the PPP frames only. The air link overhead, or any overheadimposed by RLP, etc. and is not counted.

[0253] 4. Accounting Authentic. See Radius Acct-Authentic attribute. Thevalue of this attribute is Local or Remote depending on whether theserving IWF or the home IWF generates the accounting record.

[0254] 5. Accounting Session Time. See Radius Acct-Session-Timeattribute. This attribute indicates the amount of time that the user hasbeen receiving service. If sent by the serving IWF, this attributetracks the amount of time that the user has been receiving service fromthat serving IWF. If sent by the home IWF, this attribute tracks theamount of time that the user has been receiving service from the homeIWF.

[0255] 6. Accounting Input Packets. See Radius Acct-Input-Packetsattribute. This attribute indicates the number of packets received fromthe end system. For a serving IWF, this attribute tracks the number ofPPP frames input into the serving IWF from an end system. For a homeIWF, this attribute tracks the number of PPP frames input into the homeIWF from an end system.

[0256] 7. Accounting Output Packets. See Radius Acct-Output-Packetsattribute. This attribute indicates the number of packets sent to theend system. For a serving IWF, this attribute tracks the number of PPPframes output by the serving IWF to the end system. For a home IWF, thisattribute tracks the number of PPP frames sent to the end system fromthe home IWF.

[0257] 8. Accounting Terminate Cause. See Radius Acct-Terminate-Causeattribute. This attribute indicates the reason why a user session wasterminated. In addition, a specific cause code is also present toprovide additional details. This attribute is only present in accountingreports at the end of the session.

[0258] 9. Network Accounting Terminate Cause. This attribute indicates adetailed reason for terminating a session. This specific attribute isencoded as a vendor specific attribute and is only reported in a RadiusAccounting attribute at the end of session. The standard Radiusattribute Acct-Terminate-Cause is also present. This attribute providesspecific cause codes, not covered by the Acct-Terminate-Cause attribute.

[0259] 10. Network Air link Access Protocol. This attribute indicatesthe air link access protocol used by the end system. This attribute isencoded as a vendor specific attribute.

[0260] 11. Network Backhaul Access Protocol. This attribute indicatesthe backhaul access protocol used by the access point to ferry data toand from the end system. This attribute is encoded as a vendor specificattribute.

[0261] 12. Network Agent Machine Name. This attribute is the fullyqualified domain name of the machine running the home IWF or the servingIWF. This specific attribute is encoded in vendor specific format.

[0262] 13. Network Accounting Check-point. Since the Radius accountingRFC does not define a check-point packet, the present network embodimentuses a Radius accounting start packet with this attribute to mark acheck-point. The absence of a check-point attribute means a conventionalaccounting start packet. The presence of this attribute in a accountingstart packet means a accounting check-point packet. Accounting stoppackets do not have this attribute.

[0263] In the preferred embodiment, every accounting packet and thecorresponding reply must be authenticated using MD5 and a shared secret.The IWFs are configured with a shared secret that are used by them forauthentication during communication with their Radius accounting server.The shared secrets used by the IWFs for communicating with accountingservers are stored in the home/foreign domain directory located in theMSC. The shared secrets for accounting security are communicated to theIWFs by their registration servers during the end system registrationsequence.

[0264] The accounting server software runs in a computer located in theMSC. The role of the accounting server in the system is to collect rawaccounting data from the network elements (the home and the servingIWFs), process the data and store it for transfer to the wirelessservice provider's billing system. The accounting server does notinclude a billing system. Instead, it includes support for an automaticor manual accounting data transfer mechanism. Using the automaticaccounting data transfer mechanism, the accounting server transfersaccounting records in AMA billing format to the customer's billingsystem over a TCP/IP transport. For this purpose, the system defines AMAbilling record formats for packet data. Using the manual transfermechanism, customers are able to build a tape to transfer accountingrecords to their billing system. In order to build the tape to theirspecifications, customers are provided with information to accessaccounting records so that they may process them before writing them totape.

[0265] In FIG. 22, the raw accounting data received by the accountingserver from the home or serving IWFs are processed and stored by theaccounting server. The processing done by the accounting server includesfiltering, compression and correlation of the raw accounting datareceived from the IWF. A high availability file server using dualactive/standby processors and hot swappable RAID disks is used forbuffering the accounting data while it is transiting through theaccounting server.

[0266] The accounting server delays processing of the raw accountingdata until an end system has terminated its session. When an end systemterminates its session, the accounting server processes the rawaccounting data that it has collected for the session and stores anaccounting summary record in a SQL database. The accounting summaryrecord stored in the SQL data base points to an ASN.1 encoded file. Thisfile contains detailed accounting information about the end system'ssession. The data stored in the accounting server is then transferred bythe billing data transfer agent to the customer's billing system.Alternatively, the wireless service provider may transfer the accountingdata from the SQL database and/or the ASN.1 encoded file to the billingsystem via a tape. The data base scheme and the format of the ASN.1encoded file are documented and made available to customers for thispurpose. If the volume of processed accounting data stored in theaccounting system exceeds a high water mark, the accounting servergenerates an NMS alarm. This alarm is cleared when the volume of datastored in the accounting server falls below a low water mark. The highand low water marks for generating and clearing the alarm areconfigurable. The accounting server also generates an NMS alarm if theage of the stored accounting data exceeds a configurable threshold.Conversely, the alarm is cleared, when the age of the accounting datafalls below the threshold.

[0267] The subscriber directory is used to store information aboutsubscribers and is located in the home network. The home registrationserver consults this directory during the registration phase toauthenticate and register an end system. For each subscriber, thesubscriber directory stores the following information.

[0268] 1. User-Name. This field in the subscriber record will be in SMTPformat (e.g., user@fqdn) where the user sub-field will identify thesubscriber in his or her wireless home domain and the fqdn sub-fieldwill identify the wireless home domain of the subscriber. This field issent by the end system in its registration request during theregistration phase. This field is assigned by the wireless serviceprovider to the subscriber at the time of subscription to the networkservice. This field is different than the user name field used in PPP.

[0269] 2. Mobility Security Association. This field in the subscriberrecord contains the mobility security association between the subscriberand his or her home network. As described above, a mobility securityassociation exists between each subscriber and its home registrationserver. The mobility security association defines a collection ofsecurity contexts. Each security context defines an authenticationalgorithm, an authentication mode, a shared secret, style of replayprotection and the type of encryption (including no encryption) to usebetween the end system and its home server. During registration, thehome registration server retrieves information about the subscriber'ssecurity context from the subscriber directory using the User-Name andthe security parameter index (SPI) supplied by the end system in itsregistration request. The information in the security context is usedfor enforcing authentication, encryption and replay protection duringthe session. The mobility security association is created by thewireless service provider at the time of subscription. It is up to thewireless service provider to permit the subscriber to modify thisassociation either by calling up a customer service representative or byletting subscribers access to a secure Web site. The Web site softwarewill export web pages which the wireless service provider may makeaccessible to subscribers from a secure web server. In this way,subscribers are able to view/modify the contents of the mobilitysecurity association in addition to other subscriber information thatthe service provider may make accessible.

[0270] 3 Modem MAC Address. This field contains the MAC address of themodem owned by the subscriber. In addition to the shared secret, thisfield is used during registration to authenticate the user. It ispossible to turn off MAC address based authentication on a per userbasis. The MAC address is communicated to the home registration serverduring registration.

[0271] 4. Enable MAC Address Authentication. This field is used todetermine if MAC address based authentication is enabled or disabled. Ifenabled, the home registration server checks the MAC address of theregistering end system against this field to validate the end system'sidentity. If disabled, then no checking is done.

[0272] 5. Roaming Enabled Flag. If this field is set to enabled, thenthe end system is allowed to roam to foreign networks. If this field isdisabled, then the end system is not permitted to roam to foreignnetworks.

[0273] 6. Roaming Domain List. This field is meaningful only if theRoaming Enabled Flag is set to enabled. This field contains a list offoreign domains that the end system is allowed to roam to. When thecontents of this list is null and the Roaming Enabled Flag is set toenabled, the end system is allowed to roam freely.

[0274] 7. Service Enable/Disable Flag. This field may be set to disabledby the system administrator to disable service to a subscriber. If thisfield is disabled, then the subscriber is permitted to register forservice. If the subscriber is registered and the value of this field isset to disabled, then the subscriber's end system is immediatelydisconnected by the network.

[0275] 8. Internet Service Provider Association. This field containsinformation about the subscriber's internet service provider. Thisinformation is used by the IWF during the PPP registration phase toperform authentication with the internet service provider on behalf ofthe end system and also to create a L2TP tunnel between the IWF and theinternet service provider's PPP server. This field contains the identityof the subscriber's ISP. The IWF uses this information to access the ISPdirectory for performing authentication and setting up the L2TP tunnelon behalf of the end system.

[0276] 9. Subscriber's Name & Address Information. This field containsthe subscriber's name, address, phone, fax, e-mail address, etc.

[0277] The home domain directory (HDD) is used by the registrationserver to retrieve parameters about the end system to completeregistration on behalf of the end system. Using this information, theregistration server determines if the end system is registering at homeor if the end system is a roaming end system. In the former case, theregistration server assumes the role of a home registration server andproceed with end system registration. In the latter case, theregistration server assumes the role of a foreign registration serverand, acting as a Radius proxy, it forwards the request to the real homeregistration server whose identity it gets from this directory. Forroaming end system, the parameters stored in the HDD include the IPaddress of the home registration server, the home-foreign shared secret,the home-serving IWF tunnel configuration etc. The HDD is located in theMSC.

[0278] The following information is stored in the HDD.

[0279] 1. Home Domain Name. This field is used as the key to search theHDD for an entry that matches the fully qualified home domain nameprovided by the end system in its registration request.

[0280] 2. Proxy Registration Request. This field is used by theregistration server to determine if it should act as a foreignregistration server and proxy the end system's registration request tothe real home registration server.

[0281] 3. Home Registration Server DNS Name. If the proxy registrationrequest flag is TRUE, this field is used to access the DNS name of thereal home registration server. Otherwise, this field is ignored. The DNSname is translated to an IP address by the foreign registration server.The foreign registration server uses the IP address to relay the endsystem's registration request.

[0282] 4. Foreign Domain Name. If the proxy registration request flag isTRUE, this field is used to identify the foreign domain name to the endsystem's home registration server. Otherwise, this field is ignored. Theforeign registration server uses this information to create the foreignserver machine id in SMTP format, for example, machine@fqdn. Thismachine id is sent to the home registration server by the foreignregistration server in the Radius-Access Request.

[0283] 5. Shared Secret. If the proxy registration request flag is TRUE,the shared secret is used between the foreign and home registrationservers to authenticate their identity with each other. Otherwise thisfield is ignored.

[0284] 6. Tunneling Protocol Parameters. This field is used to storeparameters to configure the tunnels to provide service to the endsystem. For an end system at home, this includes information on tunnelparameters between the base station and the home IWF and from the homeIWF to the PPP server. For a roaming end system, this includes tunnelingparameters from the base station to the serving IWF and from the servingIWF to the home IWF. At a minimum, for each tunnel, this field containsthe type of tunneling protocol to use and any tunneling protocolspecific parameters. For example, this field may contain the identifierfor the tunneling protocol L2TP and any additional parameters requiredto configure the L2TP tunnel between the IWF and its peer.

[0285] 7. Accounting Server Association. This field is used to storeinformation needed by the IWF to generate accounting data on behalf ofthe end system. It contains the name of the accounting protocol (e.g.RADIUS), the DNS name of the accounting server and additional parametersspecific to the accounting protocol like the UDP port number, the sharedsecret that the IWF must use in the Radius Accounting protocol, thefrequency of check-pointing, the seed for creating thesession/multi-session id, etc. The accounting server's DNS name istranslated to the accounting server's IP address, which is sent to theIWF.

[0286] For wireless service providers that have roaming agreements witheach other, the HDD is used for authentication and to complete theregistration process. If an end system roams from its home network to aforeign network, the foreign registration server in that networkconsults the HDD in its MSC to get information about the visiting endsystem's home registration and to authenticate the home network beforeit provides service to the visiting end system.

[0287] The software for home domain directory management preferablyprovides a graphical user interface (GUI) based HDD management interfacefor system administrators. Using this GUI, system administrators areable to view and update entries in the HDD. This GUI is not intended foruse by foreign wireless network service providers to perform remoteupdates based on roaming agreements. It is only intended for use bytrusted personnel of the home wireless service provider operating behindfire walls.

[0288] The foreign domain directory (FDD) provides functionality that isthe reverse of the home domain directory. The FDD is used by the homeregistration server to retrieve parameters about the foreignregistration server and the foreign network in order to authenticate theforeign network and create a tunnel between a serving IWF and a homeIWF. These parameters include the home-foreign shared secret, the homeIWF-serving IWF tunnel configuration, etc. The FDD is preferably locatedin the home registration server's MSC. The FDD is used by homeregistration servers for registering roaming end systems.

[0289] The following information will be stored in the FDD.

[0290] 1. Foreign Domain Name. This field is used as the key to searchthe FDD for an entry that matches the fully qualified domain name of theforeign registration server relaying the registration request.

[0291] 2. Shared Secret. This is the shared secret used between theforeign and home registration servers to authenticate their identitymutually with each other.

[0292] 3. Home IWF-Serving IWF Tunneling Protocol Parameters. This fieldis used to store parameters to configure the tunnel between the home IWFand the serving IWF. At a minimum, this field contains the type oftunneling protocol to use and any tunneling protocol specificparameters. For example, this field may contain the identifier for thetunneling protocol L2TP and any additional parameters required toconfigure the L2TP tunnel between the serving IWF and the home IWF.

[0293] 4. Accounting Server Association. This field is used to storeinformation needed by the home IWF to generate accounting data on behalfof the end system. It contains the name of the accounting protocol (e.g.RADIUS), the DNS name of the accounting server and additional parametersspecific to the accounting protocol like the UDP port number, the sharedsecret that the IWF must use in the Radius Accounting protocol, thefrequency of check-pointing, the seed for creating thesession/multi-session id, etc. The accounting server's DNS name istranslated to the accounting server's IP address, which is sent to theforeign agent.

[0294] For wireless service providers that have roaming agreements witheach other, the FDD is used to do authentication and complete theregistration process. If an end system roams from its home network to aforeign network, the registration server in the home network consultsthe FDD in its MSC to get information and authenticate the foreignnetwork providing service to the end system.

[0295] The foreign domain directory management software provides agraphical user interface (GUI) based FDD management interface for systemadministrators. Using this GUI, system administrators are able to viewand update entries in the FDD. This GUI is not intended for use byforeign wireless network service providers to perform remote updatesbased on roaming agreements. It is only intended for use by trustedpersonnel of the home wireless service provider operating behindfirewalls.

[0296] The internet service provider directory (ISPD) is used by thehome IWF to manage connectivity with ISPs that have service agreementswith the wireless service provider so that subscribers may access theirISPs using the network. For each subscriber, the subscriber directoryhas an entry for the subscriber's ISP. This field points to an entry inthe ISPD. The home IWF uses this information to set up the connection tothe ISP on behalf of the subscriber.

[0297] The network architecture supports roaming. In order for roamingto work between wireless service providers, the architecture mustsupport the setting up of roaming agreements between wireless serviceproviders. This implies two things: (1) updating system directoriesacross wireless service providers and (2) settlement of bills betweenservice providers.

[0298] In order to allow subscribers access to internet serviceproviders, the architecture supports roaming agreements with internetservice providers. This implies that the architecture must be able tosend data to and receive data from ISP PPP servers (i.e., that supportindustry standard protocols like PPP, L2TP and Radius). It also impliesthat the architecture handles directory updates for ISP access andsettlement of bills with ISPs.

[0299] When roaming agreements are established between two wirelessservice providers, both providers have to update their home and foreigndomain directories in order to support authentication and registrationfunctions for end systems visiting their networks from the othernetwork. At a minimum, the architecture of the present embodimentsupports manual directory updates. When a roaming agreement isestablished between two wireless service providers, then the two partiesto the agreement exchange information for populating their home andforeign domain directories. The actual updates of the directories isdone manually by the personnel of the respective service providers. Iflater, the information in the home and foreign domain directories needsto be updated, the two parties to the agreement exchange the updatedinformation and then manually apply their updates to the directories.

[0300] In an alternative embodiment, the directory management softwareincorporates developing standards in the IETF to enable roaming betweeninternet service providers and to enable ISPs to automatically manageand discover roaming relationships. This makes manual directorymanagement no longer necessary. The network system automaticallypropagates roaming relationships, and discovers them, to authenticateand register visiting end systems.

[0301] At a minimum, the network architecture just processes and storesthe accounting data and makes the data available to the wireless serviceprovider's billing system. It is up to the billing system to handlesettlement of bills for roaming.

[0302] In an alternative embodiment, developing standards in the IETF tohandle distribution of accounting records between internet serviceproviders are incorporated into the network architecture to enable ISPsto do billing settlement for roaming end systems.

[0303] The system software supports access to ISPs and private intranetsby supporting L2TP between the home IWF and the ISPs or intranet PPPserver. The internet service provider directory contains informationuseful to the IWF for creating these tunnels. As access agreementsbetween the wireless service provider and internet service providers areput in place, this directory is updated manually by the wireless serviceprovider's personnel. Automatic updates and discovery of accessrelationships between the wireless service provider and internet serviceproviders are presently contemplated and implemented as the internetstandards evolve. While accessing an internet service provider, thesubscriber receives two bills—one from the wireless service provider forthe use of the wireless network and the second from the internet serviceprovider. Although common billing that combines both types of charges isnot handled by the minimum embodiment software, it is contemplated thatthe software will take advantage of internet standards for billingsettlement as they evolve so that subscribers may receive a common billbased on roaming agreements between the ISP and wireless serviceproviders.

[0304] The system includes a element management system for managing thenetwork elements. From the element manager, system administratorsperform configuration, performance and fault/alarm management functions.The element management applications run on top of a web browser. Using aweb browser, system administrators manage the network from anywhere thatthey have TCP/IP access. The element manager also performs an agent rolefor a higher level manager. In this role it exports an SNMP MIB foralarm and fault monitoring.

[0305] A higher level SNMP manager is notified of alarm conditions viaSNMP traps. The higher level SNMP manager periodically polls the elementmanager's MIB for the health and status of the network. Systemmanagement personnel at the higher level manager are able to view anicon representation of the network and its current alarm state. Bypointing and clicking on the network element icon, systems managementpersonnel execute element management applications using a web browserand perform more detailed management functions.

[0306] Inside the network, management of the physical and logicalnetwork elements is performed using a combination of the SNMP protocoland internal management application programming interfaces. Applicationsin the element manager use SNMP or other management APIs to performnetwork management functions.

[0307] Architecturally, the element management system includes twodistinct sets of functional elements. The first set of functionalelements, including the configuration data server, performance datamonitor and health/status monitor and network element recovery software,executes on an HA server equipped with RAID disks. The second set offunctional elements, including the management applications, executes ona dedicated, non-HA management system. Even if the element managersystem becomes non-operational, the network elements continue to be ableto run and report alarms and even be able to recover from faultconditions. However, since all the management applications execute inthe non-HA element manager, if the element manager goes down, thenrecovery actions requiring human intervention are not possible until theelement manager becomes operational.

[0308] The wireless hubs (WHs) in the base stations are typically ownedby a wireless service provider (WSP), and they are connected to theWSP's registration server (RS) either via point-to-point links,intranets or the Internet. The WSP's registration server is typically asoftware module executing on a processor to perform certain registrationfunctions. Inter-working function units (IWF units) are typicallysoftware modules executing on a processor to perform certain interfacingfunctions. IWF units are typically connected to the registration serversvia intranets/WAN, and the IWF units are typically owned by the WSP.However, the IWF units need not be located within the same LAN as theregistration servers. Typically, accounting and directory servers (alsosoftware modules executing on a processor) are connected to theregistration servers via a LAN in the service provider's Data Center(e.g., a center including one or more processors that hosts variousservers and other software modules). Traffic from the end system is thenrouted via a router (connected to the LAN) to the public Internet or toan ISP's intranet.

[0309] The registration server located in a foreign WSP's network isreferred to as the foreign registration server (FRS), and theregistration server located in the end system's home network (where themobile purchases its service) is referred to as the home registrationserver (HRS). The inter-working function unit in the home network isreferred to as the home IWF while the inter-working function unit in theforeign network (i.e., the network the end system is visiting) isreferred to as the serving IWF.

[0310] For fixed wireless service (i.e., a non-moving end system), anend system may register for service on the home network from the homenetwork (e.g., at home service) or from a foreign network (e.g., roamingservice). The end system receives an advertisement sent by an agent(e.g., an agent function implemented in software) in the wireless hubvia the access point. There are both MAC-layer registration as well asnetwork-layer registration to be accomplished. These may be combinedtogether for efficiency.

[0311] For end systems at home (FIG. 23), the network layer registration(like a local registration) make's known to the home registration serverthe wireless hub to which the end system is currently attached. An IWFin the end system's home network will become the anchor or home IWF.Thus, PPP frames to and from the end system travel via the wireless hubto the home IWF in the home network. If the end system is at home, thehome IWF is connected to the wireless hub via an XTunnel protocol.

[0312] For roaming wireless service (FIG. 24), the foreign registrationserver determines the identity of the home network of the roaming endsystem during the registration phase. Using this information, theforeign registration server communicates with the home registrationserver to authenticate and register the end system. The foreignregistration server then assigns a serving IWF, and an I-XTunnelprotocol connection is established between the home IWF and the servingIWF for the roaming end system. The serving IWF relays frames betweenthe wireless hub and the home IWF. From the home IWF, data is sent to aPPP server (i.e., point-to-point protocol server) which may reside inthe same IWF. However, if the data is to go to a corporate intranet oran ISP's intranet that has its own PPP server, the data is sent to theseparate PPP server via the L2TP protocol. The separate server istypically owned and operated by an Internet service provider who isdifferent from the wireless service provider. For the duration of thesession, the locations of the home IWF and PPP server remain fixed. TheMAC layer registration can be combined with the network registration toeconomize on the overhead of separate communications for MAC layer andnetwork layer registration; however, it may be advantageous to notcombine these registration processes so that the WSP's equipment will beinteroperable with other wireless networks that supports pure IETFMobile-IP.

[0313] Registration sets up three tables. Table 1 is associated witheach access point, and Table 1 identifies each connection (e.g., eachend system) by a connection id (CID) and associates the connection idwith a particular wireless (WM) modem address (i.e., the address of theend system or end system). Table 2 is associated with each wireless hub(WH), and Table 2 associates each connection id with a correspondingwireless modem address, access point and XTunnel id (XID). Table 3 isassociated with each inter-working function (IWF), and Table 3associates each connection id with a corresponding wireless modemaddress, wireless hub address, XTunnel id and IP port (IP/port). Theentries described for these tables are described to include onlyrelevant entries that support the discussion of mobility management. Inreality, there are other important fields that need to be included aswell. TABLE 1 Connection Table at AP CID WM C1 WM1 C2 WM1 C1 WM2

[0314] TABLE 2 Connection Table at WH CID WM AP XID C1 WM1 AP1 5 C2 WM1AP1 5 C1 WM2 AP1 6 C1 WM3 AP2 7

[0315] TABLE 3 Connection Table at IWF CID WM WH XID IP/Port C1 WM1 WH15 IP1/P1 C2 WM1 WH1 5 IP1/P2 C1 WM2 WH1 6 IP2/P3 C1 WM3 WH1 7 IP3/P1 C5WM5 WH2 8 IP4/P1

[0316] The protocol stacks for dial-up users at home in a network aswell as roaming users are illustrated in FIGS. 25-28. FIG. 25 depictsprotocol stacks used for direct internet access by a fixed (i.e.,non-moving) end system at home where a PPP protocol message terminatesin the home IWF (typically collocated with the wireless hub) whichrelays message to and from an IP router and from there to the publicinternet. FIG. 26 depicts protocol stacks used for remote intranetaccess (i.e., either private corporate nets or an ISP) by a fixed (i.e.,non-moving) end system at home where a PPP protocol message is relayedthrough the home IWF (typically collocated with the wireless hub) to aPPP server of the private corporate intranet or ISP. FIG. 27 depictsprotocol stacks used for direct internet access by a roaming but fixed(i.e., non-moving) or a moving end system where the PPP protocolterminates in the home IWF (typically located in a mobile switchingcenter of the home network) which relays message to and from an IProuter. In FIG. 27, note how message traffic passes through a servingIWF (typically collocated with the wireless hub) in addition to the homeIWF. FIG. 28 depicts protocol stacks used for remote intranet access(i.e., either private corporate nets or an ISP) by a roaming but fixed(i.e., non-moving) or a moving end system where a PPP protocol messageis relayed through the home IWF (typically located in a mobile switchingcenter of the home network) to a PPP server of the private corporateintranet or ISP. In FIG. 28, note how message traffic passes through aserving IWF (typically collocated with the wireless hub) in addition tothe home IWF. When the serving IWF and the wireless hub are co-locatedin the same nest of computers or are even programmed into the samecomputer, it is not necessary to establish a tunnel using the XTunnelprotocol between the serving IWF and the wireless hub.

[0317] Equivalent variations to these protocol stacks (e.g. the RLP canbe terminated at the wireless hub rather than at the serving IWF or homeIWF for mobiles at home) are also envisioned. If the IWF is located farfrom the wireless hub, and the packets can potentially be carried over alossy IP network between the IWF and wireless hub, then it would bepreferred to terminate the RLP protocol at the wireless hub. Anothervariation is the Xtunnel between wireless hub and IWF need not be builton top of the UDP/IP. Xtunnels can be built using the Frame Relay/ATMlink layer. However, the use of UDP/IP makes it easier to move thewireless hub and IWF software from one network to another.

[0318] Furthermore, the PPP protocol can be terminated in a wirelessmodem and sent to one or more endsystems via an ethernet connection. Asillustrated in FIG. 29, the wireless modem 300 receives the PPP protocolinformation and encapsulates the PPP payload in an ethernet frame to betransported to at least one of the end systems 304 and 306 via theinternet connection 302.

[0319] DIX ethernet can be used for encapsulating the XWD MAC primitivesbut the system is not limited thereto. The ethernet frame format for XWDcontrol frames is illustrated in FIG. 30. The ethernet header contains adestination address, a source address and an ethernet type field. Thedestination address field contains the ethernet address of the MACentity to which the primative is being sent. For MAC primitives invokedby the MAC user, this field will contain the ethernet address of the MACuser. For broadcast primitives, this address will be the ethernetbroadcast address. The source address field contains the ethernetaddress of the MAC entity invoking the primitive. The ethernet typefield contains the ethernet type for XWD. Possible values areXWD_Control for control frames and XWD_Data for data frames. Thesevalues must be different from all the ethernet type values that havebeen stnadardized and must be registered with the controlling authority.

[0320] The ethernet frame then has an XWD header field. The XWD headercan be 16 bits long and will only be present for XWD control frames. Thefields are illustrated in FIG. 31. The ethernet frame also contains aprotocol header, a PPP payload field and a XWD MAC field. The headervalues for primitives using ethernet encapsulation are illustrated inTable 4 below. XWD MAC Primitive Destination Source Ethernet Prim- NameAddress Address Type itive M_Discover.Req Broadcast or MAC UserXWD_Control 0 unicast MAC Providider M_Discover.Cnf MAC User MACProvider XWD_Control 1 M_OpenSap.Req MAC MAC User XWD_Control 2 ProviderM_OpenSap.Cnf MAC User MAC Provider XWD_Control 3 M_CloseSap.Req MAC MACUser XWD_Control 4 Provider M_CloseSap.Cnf MAC User MAC ProviderXWD_Control 5 M_EchoSap.Req MAC User MAC Provider XWD_Control 6M_EchoSap.Cnf MAC MAC User XWD_Control 7 Provider M_Connect.Req MAC MACUser XWD_Control 8 Provider (end system (modem only) only) M_Connect.IndMAC User MAC Provider XWD_Control 9 (wireless hub (AP only) only)M_Connect.Rsp MAC MAC User XWD_Control 10 Provider (wireless hub (APonly) only) M_Connect.Cnf MAC User MAC Provider XWD_Control 11 (endsystem (modem only) only) M_Disconect. MAC MAC User XWD_Control 12 ReqProvider

[0321] In another alternative, the PPP protocol can be terminated in awireless router and then sent on to at least one end system connected toa local area network (LAN). As illustrated in FIG. 32, the wirelessrouter 350 receives the PPP protocol information via the wireless modem352. The router 354 receives the PPP information from the wireless modem352 and sends the PPP information to at least one of the end systems356, 358, 360 via a LAN link 362.

[0322] Four types of handoff scenarios may occur, and they are labeled:(i) local mobility, (ii) micro mobility, (iii) macro mobility, and (iv)global mobility. In all four scenarios (in one embodiment of theinvention), a route optimization option is not considered so that thelocations of the home registration server and the ISP's PPP server donot change. In another embodiment of the system with route optimization,the ISP's PPP server may change. However, this aspect is discussedbelow. In addition, the locations of the foreign registration server andIWF do not change in the first three scenarios.

[0323] The proposed IETF Mobile IP standard requires that whenever anend system changes the IP subnet to which it is attached, it sends aregistration request message to a home agent in its home subnet. Thismessage carries a care-of address where the end system can be reached inthe new subnet. When traffic is sent, for example, from an ISP to an endsystem, the home agent intercepts the traffic that is bound for the endsystem as it arrives in the home subnet, and then forwards the trafficto the care-of address. The care-of address identifies a particularforeign agent in the foreign subnet. An end system's foreign agent canreside in the end system itself, or in a separate node that in turnforwards traffic to the end system (i.e., proxy registration agent).Mobile IP handoffs involve exchange of control messages between an endsystem's agent, the end system's home agent and potentially itscorresponding hosts (CHs) (with route optimization option).

[0324] The proposed IETF Mobile IP standard would find it difficult tomeet the latency and scalability goals for all movements in a largeinternetwork. However, the present hierarchical mobility managementmeets such goals. For small movements (e.g. a change of Access Points),only MAC-layer re-registrations are needed. For larger movements,network-layer re-registrations are performed. The present hierarchicalmobility management is different from the flat-structure used in theIETF proposed Mobile-IP standard as well as the serving/anchorinter-working function model used in cellular systems like CDPD (basedon a standard sponsored by the Cellular Digital Packet Data forum).

[0325] As depicted in FIG. 33, the local mobility handoff handles endsystem (designated MN for mobile node) movement between APs that belongto the same wireless hub. Thus, only MAC layer re-registration isrequired. The end system receives a wireless hub advertisement from anew AP and responds with a registration request addressed to the new AP.

[0326] The new AP (i.e., the one that receives the registration requestfrom the end system) creates new entries in its connection table andrelays the registration message to its wireless hub. In local mobilityhandoffs, the wireless hub does not change. The wireless hub recognizesthe end system's registration request as a MAC level registrationrequest, and it updates its connection table to reflect the connectionto the new AP. Then, the old AP deletes the connection entry from itsconnection table. There are at least three ways whereby the old AP candelete the old entries, namely (i) upon time out, (ii) upon receiving acopy of the relayed MAC layer association message from the new AP to thewireless hub (if this relay message is a broadcast message), and (iii)upon being informed by the wireless hub of the need to delete the entry.

[0327] As depicted in FIG. 34, the micro mobility handoff handles endsystem (designated MN for mobile node) movement between wireless hubsthat belong to the same registration server and where the end system canstill be served by the existing serving IWF. When an advertisement isreceived from a new wireless hub (through a new AP), the end systemsends a message to request registration to the registration server. Theregistration request is relayed from the new AP to the new wireless hubto the registration server.

[0328] When the registration server determines that the existing IWF canstill be used, the registration server sends a build XTunnel Requestmessage to request the existing IWF to build an XTunnel to the newwireless hub. Later, the registration server sends a tear down XTunnelrequest message to request the existing IWF to tear down the existingXTunnel with the old wireless hub. The build and tear XTunnel Requestmessages can be combined into one message. A foreign registration serverdoes not forward the registration message to the home registrationserver since there is no change of IWF, either the serving IWF or homeIWF.

[0329] Upon receiving a positive build XTunnel reply and a positive tearXTunnel reply from IWF, the registration server sends a registrationreply to end system. As the registration reply reaches the new wirelesshub, the connection table at the new wireless hub is updated to reflectthe connection to the new AP. The new AP updates its MAC filter addresstable and connection table after receiving a message from the newwireless hub, and the registration reply is forwarded to the end system.

[0330] The registration server sends a release message to the oldwireless hub. When the old wireless hub receives the release message, itupdates its connection table and the MAC filter address table andconnection table of the old AP.

[0331] As depicted in FIG. 35, the macro mobility handoff case handlesmovement between wireless hubs that involves a change of the serving IWFin the foreign network, but it does not involve a change in theregistration server. When an advertisement is received from a newwireless hub (through a new AP), the end system sends a message torequest a network layer registration to the registration server. Theregistration request is relayed from the new AP to the new wireless hubto the registration server.

[0332] The registration server recognizes that it is a foreignregistration server when the end system does not belong to the presentregistration server's network. This foreign registration serverdetermines the identity of the home registration server by using arequest, preferably a Radius Access request (RA request), to the foreigndirectory server (like a big yellow pages) and then assigns anappropriate IWF to be the serving IWF, and it forwards a registrationrequest to the home registration server, preferably through a RadiusAccess request (RA request), informing the home registration server ofthe newly selected IWF.

[0333] The home registration server authenticates the registrationrequest by using a request, preferably a Radius Access request (RArequest), to the home directory server. Upon authenticating the requestand determining that the existing home IWF can still be used, the homeregistration server instructs the home IWF to build a new I-XTunnel tothe newly assigned serving IWF and to tear down the existing I-XTunnelto the old serving IWF. Upon receiving a positive build I-XTunnel replyand a positive tear I-XTunnel reply from the home IWF, the homeregistration server sends a registration reply to the foreignregistration server.

[0334] The foreign registration server then instructs the newly assignedIWF to build an XTunnel to the new wireless hub. Upon receiving apositive build XTunnel reply, the foreign registration server instructsthe old IWF to tear down the XTunnel to the old wireless hub. Uponreceiving a positive build XTunnel reply and a positive tear XTunnelreply, the foreign registration server sends a registration reply to endsystem.

[0335] As the registration reply reaches the new wireless hub, theconnection table at the new wireless hub is updated to reflect theconnection to the new AP. The new AP updates its MAC filter addresstable and connection table after receiving a message from the newwireless hub, and the registration reply is forwarded to the end system.

[0336] The registration server sends a release message to the oldwireless hub. When the old wireless hub receives the release message, itupdates its connection table and the MAC filter address table, and theold AP updates its MAC filter address table and connection table afterreceiving a message from the old wireless hub.

[0337] The global mobility handoff case handles movement betweenwireless hubs that involves a change of registration servers. FIG. 36depicts a global mobility handoff where the home IWF does not change,and FIG. 37 depicts a global mobility handoff where the home IWFchanges. When an advertisement is received from a new wireless hub(through a new AP) in a new foreign network, the end system sends amessage to request a network layer registration to the new foreignregistration server. The registration request is relayed from the new APto the new wireless hub to the new foreign registration server.

[0338] The registration server recognizes that it is a new foreignregistration server when the end system does not belong to the presentregistration server's network. This foreign registration serverdetermines the identity of the home registration server by using arequest, preferably a Radius Access request (RA request), to the foreigndirectory server (like a big yellow pages) and then assigns anappropriate IWF to be the serving IWF, and it forwards the registrationrequest to the home registration server, preferably through a RadiusAccess request (RA request), informing the home registration server ofthe newly selected IWF.

[0339] The home registration server authenticates the registrationrequest by using a request, preferably a Radius Access request (RArequest), to the home directory server. Upon authenticating the requestand determining that the existing home IWF can still be used (FIG. 36),the home registration server instructs the home IWF to build a newI-XTunnel to the serving IWF newly assigned by the new foreignregistration server. The home registration server also sends ade-registration message to the old foreign registration server andinstructs the home IWF to tear down the existing I-XTunnel to theexisting serving IWF of the old foreign network. Upon receiving apositive build I-XTunnel reply and a positive tear I-XTunnel reply fromthe home IWF, the home registration server sends a registration reply tothe new foreign registration server.

[0340] The new foreign registration server then instructs the newlyassigned IWF to build an XTunnel to the new wireless hub. Upon receivinga positive build XTunnel reply, the foreign registration server sends aregistration reply to end system. As the registration reply reaches thenew wireless hub, the connection table at the new wireless hub isupdated to reflect the connection to the new AP. The new AP updates itsMAC filter address table and connection table after receiving a messagefrom the new wireless hub, and the registration reply is forwarded tothe end system.

[0341] The old foreign registration server instructs the old IWF to teardown the XTunnel to the old wireless hub. Upon receiving a positive tearXTunnel reply or contemporaneously with the tear down XTunnel request,the old foreign registration server sends a release message to the oldwireless hub. When the old wireless hub receives the release message, itupdates its connection table and the MAC filter address table, and theold AP updates its MAC filter address table and connection table afterreceiving a message from the old wireless hub.

[0342] Alternatively, after the home registration server authenticatesthe registration request from the new foreign registration server anddetermines that the existing home IWF cannot be used (FIG. 37), the homeregistration server chooses a new home IWF and instructs the new homeIWF to build a new level 2 tunnel protocol tunnel (L2TP tunnel) to thepresent PPP server (e.g., the PPP server in a connected ISP intranet).Then, the home registration server instructs the old home IWF totransfer its L2TP tunnel traffic to the new home IWF.

[0343] Then the home registration server instructs the new home IWF tobuild a new I-XTunnel to the serving IWF newly assigned by the newforeign registration server. The home registration server also sends ade-registration message to the old foreign registration server andinstructs the home IWF to tear down the existing I-XTunnel to theexisting serving IWF of the old foreign network. Upon receiving apositive build I-XTunnel reply and a positive tear I-XTunnel reply fromthe home IWF, the home registration server sends a registration reply tothe new foreign registration server.

[0344] The new foreign registration server then instructs the newlyassigned IWF to build an XTunnel to the new wireless hub. Upon receivinga positive build XTunnel reply, the foreign registration server sends aregistration reply to end system. As the registration reply reaches thenew wireless hub, the connection table at the new wireless hub isupdated to reflect the connection to the new AP. The new AP updates itsMAC filter address table and connection table after receiving a messagefrom the new wireless hub, and the registration reply is forwarded tothe end system.

[0345] The old foreign registration server instructs the old IWF to teardown the XTunnel to the old wireless hub. Upon receiving a positive tearXTunnel reply or contemporaneously with the tear down XTunnel request,the old foreign registration server sends a release message to the oldwireless hub. When the old wireless hub receives the release message, itupdates its connection table and the MAC filter address table, and theold AP updates its MAC filter address table and connection table afterreceiving a message from the old wireless hub.

[0346] End systems constructed according to the present systeminteroperate with networks constructed according to the proposed IETFMobile-IP standards, and end systems constructed according to theproposed IETF Mobile-IP standards interoperate with networks constructedaccording to the present invention.

[0347] Differences between the present system and the IETF Mobile-IP(RFC2002, a standards document) include:

[0348] (i) The present systemists a hierarchical concept for mobilitymanagement rather than a flat structure as in the proposed IETFMobile-IP standard. Small mobility within a small area does not resultin a network level registration. Micro mobility involves setting up of anew Xtunnel and tearing down of an existing Xtunnel. Global mobility, atthe minimum, involves setting up of a new I-XTunnel and tearing down ofan existing I-Xtunnel apart from the setting up/tearing down of XTunnel.Global mobility sometimes also involves setting up a new L2TP Tunnel andtransferring of L2TP state from the existing L2TP Tunnel to the new L2TPTunnel.

[0349] (ii) In the present invention, a user name plus a realm is usedto identify a remote dial-up user rather than a fixed home address as inthe case of the proposed IETF Mobile-IP standard.

[0350] (iii) In the present invention, registration and routingfunctions are carried out by separate entities. The two functions arecarried out by the home agent in the proposed IETF Mobile IP standard,and both functions are carried out by the foreign agent in the proposedIEFT Mobile IP standard. In contrast, in an embodiment of the presentinvention, registration is carried out in the registration server androuting functions are carried out by both the home and foreign IWF andthe wireless hub (also referred to as the access hub).

[0351] (iv) The present system utilizes three tunnels per PPP session.The XTunnel is more of a link-layer tunnel between the wireless hub andthe serving IWF. The I-XTunnel between the serving IWF and the home IWFis more like the tunnel between home and foreign agents in the proposedIETF Mobile-IP standard. But it also has additional capabilities beyondthe tunnels proposed by the Mobile-IP standard. The L2TP tunnel is usedonly when home IWF is not a PPP server. The number of these tunnels maybe reduced by combining some functions in the same nodes as describedearlier.

[0352] (v) In the present invention, wireless registration occurs beforePPP session starts while in the proposed IETF Mobile-IP standard,Mobile-IP registration occurs after PPP session enters into the openstate.

[0353] (vi) In the present invention, the network entity that advertisesthe agent advertisement (i.e., the wireless hub) is not on a direct linkto the end systems whereas for the proposed IETF Mobile-IP standard, theagent advertisement must have a TTL of 1 which means that the endsystems have a direct link with the foreign agent. In addition, theagent advertisement in the present systems not an extension to the ICMProuter advertisements as in the proposed IETF Mobile-IP standard.

[0354] End systems in the present invention, should support agentsolicitation. When an end system in the present system visits a networkwhich is supporting the proposed IETF Mobile-IP standard, it waits untilit hears an agent advertisement. If it does not receive an agentadvertisement within a reasonable time frame, it broadcasts an agentsolicitation.

[0355] In the present invention, network operators may negotiate withother networks that support the proposed IETF Mobile-IP standard suchthat home addresses can be assigned to the end systems of the presentsystem that wish to use other networks. When the end system of thepresent system receives the agent advertisement, it can determine thatthe network it is visiting is not an a network according to the presentsystem and hence uses the assigned home address to register.

[0356] For networks supporting the proposed IETF Mobile-IP standard, thePPP session starts before Mobile-IP registration, and the PPP server isassumed to be collocated with the foreign agent in such networks. In oneembodiment, an SNAP header is used to encapsulate PPP frames in the MACframes of the present system (in a manner similar to Ethernet format),and the foreign agent interprets this format as a proprietary PPP formatover Ethernet encapsulation. Thus, the end system of the present systemand its PPP peer can enter into an open state before the foreign agentstarts transmitting an agent advertisement, and the end system of thepresent system can register.

[0357] To allow end systems supporting the proposed IETF Mobile-IPstandard to work in networks of the type of the present invention, suchmobiles are at least capable of performing similar MAC layerregistrations. By making the agent advertisement message format similarto the proposed Mobile-IP standard agent advertisement message format, avisiting end system can interpret the agent advertisement and registerwith a wireless hub. In the present invention, registration request andreply messages are similar to the proposed IETF Mobile-IP standardregistration request and reply messages (without any unnecessaryextensions) so that the rest of the mobility management features of thepresent system are transparent to the visiting end systems.

[0358] Since end systems supporting the proposed IETF Mobile-IP standardexpect a PPP session to start before Mobile-IP registration, an optionalfeature in wireless hubs of the present system starts to interpret PPPLCP, NCP packets after MAC-layer registrations

[0359] To avoid losing traffic during handoffs, the mobility managementof the present systemists the make before break concept. For localmobility, a make before break connection is achieved by turning theMAC-layer registration message relayed by the new AP to the wireless hubinto a broadcast message. That way, the old AP can hear about the newregistration and forward packets destined for the end system that havenot been transmitted to the new AP.

[0360] For micro mobility, information about the new wireless hub isincluded in the Tear XTunnel message exchanged between the serving IWFand the old WH. That way, the old wireless hub can forward bufferedpackets to the new wireless hub upon hearing a TearXTunnel message fromthe serving IWF. Alternatively, the RLP layer at the IWF knows thesequence number that has been acknowledged by the old wireless hub sofar.

[0361] At the same time, the IWF knows the current send sequence numberof the latest packet sent to the old wireless hub. Therefore, the IWFcan forward those packets that are ordered in between these two numbersto the new wireless hub before sending newer packets to the new wirelesshub. The RLP layer is assumed to be able to filter duplicate packet. Thesecond approach is probably preferable to the first approach for the oldwireless hub may not be able to communicate with one another directly.

[0362] For macro mobility, the old serving IWF can forward packets tothe new serving IWF, in addition to the packet forwarding done from theold wireless hub to the new wireless. All we need to do is to forwardthe new serving IWF identity to the new serving IWF in the tear downI-XTunnel message. Another way to achieve the same result is to let thehome IWF forward the missing packets to the new serving IWF rather thanasking the old serving IWF to do the job since the home IWF knows theI-XTunnel sequence number last acknowledged by the old serving IWF andthe current I-XTunnel sequence number sent by the home IWF.

[0363] The method of estimating how much buffer should be allocated permobile per AP per wireless hub per IWF such that the traffic lossbetween handoffs can be minimized is to let the end system for the APfor the wireless hub for the IWF estimate the packet arrival rate andthe handoff time. This information is passed to the old AP of thewireless hub of the IWF to determine how much traffic should betransferred to the new AP of the wireless hub of the IWF, respectively,upon handoffs.

[0364] To achieve route optimization in the present invention, the endsystem chooses the PPP server closest to the serving IWF. Without routeoptimization, excessive transport delays and physical line usage may beexperienced.

[0365] For example, an end system subscribed to a home network in NewYork City may roam to Hong Kong. To establish a link to a Hong Kong ISP,the end system would have a serving IWF established in a wireless hub inHong Kong and a home IWF established in the home network in New YorkCity. A message would then be routed from the end system (roamed to HongKong) through the serving IWF (in Hong Kong) and through the home IWF(in New York City) and back to the Hong Kong ISP.

[0366] A preferred approach is to connect from the serving IWF (in HongKong) directly to the Hong Kong ISP. The serving IWF acts like the homeIWF. In this embodiment, roaming agreements exist between the home andforeign wireless providers. In addition, the various accounting/billingsystems communicate with one another automatically such that billinginformation is shared. Accounting and billing information exchange maybe implemented using standards such as the standard proposed by theROAMOPS working group of the IETF.

[0367] However, the serving IWF must still discover the closest PPPserver (e.g., the Hong Kong ISP). In the present embodiment, the foreignregistration server learns of the end system's desire to connect to aPPP server (e.g., a Hong Kong ISP) when it receives a registrationrequest from the end system. When the foreign registration serverdetermines that the serving IWF is closer to the desired PPP server(e.g., the Hong Kong ISP) than the home IWF is, the foreign registrationserver instructs the serving IWF to establish an L2TP tunnel to itsnearest PPP server (in contrast to the PPP server closest to the homeregistration server and home IWF). Then, the foreign registration serverinforms the home registration server that the end system is being servedby the serving IWF and the foreign PPP.

[0368] In an alternative embodiment, the foreign registration serverdetermines that the serving IWF is closer to the desired PPP server(e.g., the Hong Kong ISP) than the home IWF is, when it receives aregistration request from the end system. The foreign registrationserver relays the registration request message to the home registrationserver with an attached message indicating the serving IWF informationand a notification that route optimization is preferred. At the sametime, the foreign registration server instructs the serving IWF toestablish an L2TP tunnel to the PPP server. Upon approving theregistration request, the home registration server instructs the homeIWF to transfer the L2TP state to the foreign IWF.

[0369] Having described preferred embodiments of a novel networkarchitecture with wireless end users able to roam (which are intended tobe illustrative and not limiting), it is noted that modifications andvariations can be made by persons skilled in the art in light of theabove teachings. For example, connection links described herein may makereference to known connection protocols (e.g., IP, TCP/IP, L2TP, IEEE802.3, etc.); however, the system contemplates other connectionprotocols in the connections links that provide the same or similar datadelivery capabilities. Acting agents in the above described embodimentsmay be in the form of software controlled processors or may be otherform of controls (e.g., programmable logic arrays, etc.). Acting agentsmay be grouped as described above or grouped otherwise in keeping withthe connection teachings described herein and subject to security andauthentication teachings as described herein. Furthermore, a singleaccess point, access hub (i.e., wireless hub) or inter-working functionunit (IWF unit) may provide multi-channel capability. Thus, a singleaccess point or access hub or IWF unit may act on traffic from multipleend systems, and what is described herein as separate access points,access hubs or IWF units contemplates equivalence with a singlemulti-channel access point, access hub or IWF unit. It is therefore tobe understood that changes may be made in the particular embodiments ofthe system disclosed which are within the scope and spirit of thesystems defined by the appended claims.

[0370] Having thus described the system with the details andparticularity required by the patent laws, what is claimed and desiredprotected by letters patent is set forth in the appended claims.

What is claimed is:
 1. A wireless data network comprising: a homenetwork that includes a home mobile switching center, a wireless modemand at least one end system, wherein said wireless modem and said atleast one end system are connected together via an ethernet link; and aPPP server, wherein PPP information sent from said PPP server for saidat least one end system is encapsulated by the wireless modem in anethernet frame and sent to said at least one end system via saidethernet link.
 2. The network according to claim 1, wherein PPPinformation from said at least one end system is sent to the wirelessmodem via the ethernet link and then trnasmitted from the wireless modemto the PPP server.
 3. The network according to claim 1, wherein saidhome switching center includes a home inter-working function.
 4. Thenetwork according to claim 3, wherein PPP information from said PPPserver is transmitted through the home inter-working function to thewireless modem.
 5. The network according to claim 4, wherein PPPinformation from said at least one end system is sent to the wirelessmodem via the ethernet link and then transmitted from the wireless modemto the PPP server through the home inter-working function.